From 30d94536a9fb1b59f6752ecb4954e9a84bf57fb9 Mon Sep 17 00:00:00 2001
From: rus07tam <rus07tam.uwu@gmail.com>
Date: Wed, 6 May 2026 12:21:06 +0300
Subject: [PATCH] release 0.1.0

---
 .gitignore                    |    3 +
 Cargo.lock                    | 1217 +++++++++++++++++++++++++++++++++
 Cargo.toml                    |   40 ++
 LICENSE                       |   24 +
 README.md                     |  329 +++++++++
 benchmarks/bench.ps1          |   17 +
 benchmarks/bench.sh           |   18 +
 benchmarks/case1/main.owa     |    8 +
 benchmarks/case1/main.py      |    9 +
 benchmarks/case1/no_owu.owa   |    8 +
 benchmarks/case1/result.md    |    5 +
 flake.lock                    |  175 +++++
 flake.nix                     |   48 ++
 modules/core/assert.owa       |   17 +
 modules/core/ast.owa          |   10 +
 modules/core/branch.owa       |   12 +
 modules/core/cmp.owa          |   25 +
 modules/core/error.owa        |   22 +
 modules/core/ffi.owa          |   32 +
 modules/core/lambda.owa       |    8 +
 modules/core/loop.owa         |   23 +
 modules/core/main.owa         |   25 +
 modules/core/math.owa         |   14 +
 modules/core/scope.owa        |   22 +
 modules/core/test.owa         |   16 +
 modules/core/tests/bool.owa   |   38 +
 modules/core/tests/cmp.owa    |   41 ++
 modules/core/tests/loop.owa   |   42 ++
 modules/core/tests/main.owa   |   14 +
 modules/core/tests/map.owa    |   83 +++
 modules/core/tests/math.owa   |   40 ++
 modules/core/tests/null.owa   |    8 +
 modules/core/tests/option.owa |   33 +
 modules/core/tests/scope.owa  |   78 +++
 modules/core/tests/set.owa    |   44 ++
 modules/core/tests/str.owa    |   67 ++
 modules/core/tests/types.owa  |   53 ++
 modules/core/tests/vec.owa    |   91 +++
 modules/core/types/bool.owa   |   23 +
 modules/core/types/main.owa   |   39 ++
 modules/core/types/map.owa    |   94 +++
 modules/core/types/null.owa   |    5 +
 modules/core/types/option.owa |   26 +
 modules/core/types/set.owa    |   60 ++
 modules/core/types/str.owa    |   76 ++
 modules/core/types/struct.owa |   22 +
 modules/core/types/vec.owa    |  301 ++++++++
 modules/owu/cli/main.owa      |   19 +
 modules/owu/cli/run.owa       |   43 ++
 modules/owu/main.owa          |   15 +
 modules/std/main.owa          |    6 +
 modules/std/path.owa          |  222 ++++++
 modules/std/platform.owa      |   55 ++
 modules/std/tests/main.owa    |    3 +
 modules/std/tests/path.owa    |  286 ++++++++
 src/builtins/ast.rs           |   14 +
 src/builtins/cond.rs          |   97 +++
 src/builtins/errors.rs        |   83 +++
 src/builtins/ffi.rs           |  299 ++++++++
 src/builtins/flow.rs          |   51 ++
 src/builtins/map.rs           |   14 +
 src/builtins/math.rs          |   83 +++
 src/builtins/mod.rs           |  324 +++++++++
 src/builtins/platform.rs      |   19 +
 src/builtins/set.rs           |   47 ++
 src/builtins/str.rs           |   48 ++
 src/builtins/vec.rs           |   66 ++
 src/core/callable.rs          |  234 +++++++
 src/core/error.rs             |  207 ++++++
 src/core/interpreter.rs       |  492 +++++++++++++
 src/core/mod.rs               |   12 +
 src/core/scope.rs             |   77 +++
 src/core/special_names.rs     |   23 +
 src/core/value.rs             |  347 ++++++++++
 src/lib.rs                    |   18 +
 src/main.rs                   |   51 ++
 src/parser/annotation.rs      |   37 +
 src/parser/ast.rs             |  353 ++++++++++
 src/parser/call.rs            |   29 +
 src/parser/keyword.rs         |   14 +
 src/parser/lambda.rs          |   30 +
 src/parser/map.rs             |   39 ++
 src/parser/mod.rs             |  163 +++++
 src/parser/number.rs          |  170 +++++
 src/parser/quote.rs           |   24 +
 src/parser/set.rs             |   29 +
 src/parser/string.rs          |   96 +++
 src/parser/symbol.rs          |   22 +
 src/parser/unquote.rs         |   27 +
 src/parser/vector.rs          |   29 +
 90 files changed, 7722 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 LICENSE
 create mode 100644 README.md
 create mode 100644 benchmarks/bench.ps1
 create mode 100644 benchmarks/bench.sh
 create mode 100644 benchmarks/case1/main.owa
 create mode 100644 benchmarks/case1/main.py
 create mode 100644 benchmarks/case1/no_owu.owa
 create mode 100644 benchmarks/case1/result.md
 create mode 100644 flake.lock
 create mode 100644 flake.nix
 create mode 100644 modules/core/assert.owa
 create mode 100644 modules/core/ast.owa
 create mode 100644 modules/core/branch.owa
 create mode 100644 modules/core/cmp.owa
 create mode 100644 modules/core/error.owa
 create mode 100644 modules/core/ffi.owa
 create mode 100644 modules/core/lambda.owa
 create mode 100644 modules/core/loop.owa
 create mode 100644 modules/core/main.owa
 create mode 100644 modules/core/math.owa
 create mode 100644 modules/core/scope.owa
 create mode 100644 modules/core/test.owa
 create mode 100644 modules/core/tests/bool.owa
 create mode 100644 modules/core/tests/cmp.owa
 create mode 100644 modules/core/tests/loop.owa
 create mode 100644 modules/core/tests/main.owa
 create mode 100644 modules/core/tests/map.owa
 create mode 100644 modules/core/tests/math.owa
 create mode 100644 modules/core/tests/null.owa
 create mode 100644 modules/core/tests/option.owa
 create mode 100644 modules/core/tests/scope.owa
 create mode 100644 modules/core/tests/set.owa
 create mode 100644 modules/core/tests/str.owa
 create mode 100644 modules/core/tests/types.owa
 create mode 100644 modules/core/tests/vec.owa
 create mode 100644 modules/core/types/bool.owa
 create mode 100644 modules/core/types/main.owa
 create mode 100644 modules/core/types/map.owa
 create mode 100644 modules/core/types/null.owa
 create mode 100644 modules/core/types/option.owa
 create mode 100644 modules/core/types/set.owa
 create mode 100644 modules/core/types/str.owa
 create mode 100644 modules/core/types/struct.owa
 create mode 100644 modules/core/types/vec.owa
 create mode 100644 modules/owu/cli/main.owa
 create mode 100644 modules/owu/cli/run.owa
 create mode 100644 modules/owu/main.owa
 create mode 100644 modules/std/main.owa
 create mode 100644 modules/std/path.owa
 create mode 100644 modules/std/platform.owa
 create mode 100644 modules/std/tests/main.owa
 create mode 100644 modules/std/tests/path.owa
 create mode 100644 src/builtins/ast.rs
 create mode 100644 src/builtins/cond.rs
 create mode 100644 src/builtins/errors.rs
 create mode 100644 src/builtins/ffi.rs
 create mode 100644 src/builtins/flow.rs
 create mode 100644 src/builtins/map.rs
 create mode 100644 src/builtins/math.rs
 create mode 100644 src/builtins/mod.rs
 create mode 100644 src/builtins/platform.rs
 create mode 100644 src/builtins/set.rs
 create mode 100644 src/builtins/str.rs
 create mode 100644 src/builtins/vec.rs
 create mode 100644 src/core/callable.rs
 create mode 100644 src/core/error.rs
 create mode 100644 src/core/interpreter.rs
 create mode 100644 src/core/mod.rs
 create mode 100644 src/core/scope.rs
 create mode 100644 src/core/special_names.rs
 create mode 100644 src/core/value.rs
 create mode 100644 src/lib.rs
 create mode 100644 src/main.rs
 create mode 100644 src/parser/annotation.rs
 create mode 100644 src/parser/ast.rs
 create mode 100644 src/parser/call.rs
 create mode 100644 src/parser/keyword.rs
 create mode 100644 src/parser/lambda.rs
 create mode 100644 src/parser/map.rs
 create mode 100644 src/parser/mod.rs
 create mode 100644 src/parser/number.rs
 create mode 100644 src/parser/quote.rs
 create mode 100644 src/parser/set.rs
 create mode 100644 src/parser/string.rs
 create mode 100644 src/parser/symbol.rs
 create mode 100644 src/parser/unquote.rs
 create mode 100644 src/parser/vector.rs

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new file mode 100644
index 0000000..ecf409a
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diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..f03d9c5
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,40 @@
+[package]
+name = "owa-rs"
+version = "0.1.0"
+edition = "2024"
+repository = "https://git.ruject.fun/RuJect/owa-rs"
+description = "A Lisp-like programming language implemented in Rust"
+license = "Unlicense"
+readme = "README.md"
+categories = ["compilers", "parsing", "development-tools", "data-structures"]
+keywords = [
+  "owa",
+  "lisp",
+  "s-expression",
+  "language",
+  "interpreter",
+  "functional",
+  "persistent",
+  "immutable",
+  "ast",
+  "parser",
+  "runtime",
+  "rpds",
+]
+
+[dependencies]
+archery = "1.2.2"
+clap = { version = "4.6.1", features = ["derive"] }
+dirs = "6.0.0"
+educe = "0.6.0"
+libffi = "5.1.0"
+libloading = "0.9.0"
+nom = "8.0.0"
+num-traits = "0.2.19"
+ordered-float = { version = "5.3.0", features = ["std"] }
+paste = "1.0.15"
+reedline = "0.47.0"
+rpds = "1.2.0"
+test-case = "3.3.1"
+tracing = { version = "0.1.44", features = ["release_max_level_off"] }
+tracing-subscriber = "0.3.23"
\ No newline at end of file
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..fdddb29
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,24 @@
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this software, either in source code form or as a compiled
+binary, for any purpose, commercial or non-commercial, and by any
+means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <https://unlicense.org>
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..149faa7
--- /dev/null
+++ b/README.md
@@ -0,0 +1,329 @@
+# OWA-RS
+
+A Lisp-inspired programming language written in Rust. This is a personal learning project, so expect rough edges and experimental design.
+
+## Content
+
+- [OWA-RS](#owa-rs)
+  - [Content](#content)
+  - [Overview](#overview)
+  - [Syntax 📝](#syntax-)
+    - [Literals](#literals)
+    - [Collections](#collections)
+    - [Special Forms](#special-forms)
+    - [Comments](#comments)
+    - [Annotations](#annotations)
+    - [Example](#example)
+  - [Quick Start 🛠️](#quick-start-️)
+    - [Requirements](#requirements)
+    - [Build](#build)
+    - [Run a file](#run-a-file)
+    - [Run directly without owu](#run-directly-without-owu)
+    - [Flags](#flags)
+  - [Architecture 🏗️](#architecture-️)
+    - [Rust core](#rust-core)
+    - [Modular standard library](#modular-standard-library)
+  - [Built-in API 🔧](#built-in-api-)
+    - [Core operations](#core-operations)
+    - [Built-in namespaces](#built-in-namespaces)
+  - [Standard Library 📚](#standard-library-)
+    - [Core Library (`modules/core/`)](#core-library-modulescore)
+    - [Standard Library (`modules/std/`)](#standard-library-modulesstd)
+    - [owu (`modules/owu/`)](#owu-modulesowu)
+  - [Performance ⚡](#performance-)
+  - [Examples 🌟](#examples-)
+    - [Hello World](#hello-world)
+    - [Using Functions from Core](#using-functions-from-core)
+    - [Working with Collections](#working-with-collections)
+  - [Development 🛠️](#development-️)
+    - [Running Tests](#running-tests)
+    - [Building Documentation](#building-documentation)
+  - [TODOs 📋](#todos-)
+    - [High Priority](#high-priority)
+    - [Medium Priority](#medium-priority)
+    - [Lower Priority](#lower-priority)
+    - [Completed](#completed)
+  - [Contributing 🤝](#contributing-)
+  - [License 📄](#license-)
+
+## Overview
+
+OWA-RS is designed as a lightweight Lisp-like interpreter with:
+
+- a small Rust runtime,
+- a modular standard library,
+- a simple CLI wrapper (owu),
+- persistent immutable collections via `rpds`.
+
+> ⚠️ This is a **personal project** for learning and experimentation. It's my very first Rust project, so expect some rough edges. Use at your own risk!
+
+## Syntax 📝
+
+OWA-RS uses a familiar Lisp-style syntax with nested expressions.
+
+### Literals
+
+- Integers: `42`, `-7`
+- Floats: `3.14`, `-0.5`
+- Strings: `"hello world"`
+- Keywords: `:key`, `:value`
+- Symbols: `variable-name`, `function?`
+
+### Collections
+
+- Lists / Calls: `(function arg1 arg2)`
+- Vectors: `[1 2 3]`
+- Maps: `{:key "value" :other 42}`
+- Sets: `#{"a" "b" "c"}`
+
+### Special Forms
+
+- Lambdas: `(lambda [args] body)`
+- Macros: `(macro [args] body)`
+- Quotes: `'expression`
+- Unquotes: `$expression`
+
+### Comments
+
+Comments start with `;;` and continue to the end of the line.
+
+### Annotations
+
+Annotations are placed in angle brackets (`<annotation>value`) and can contain any value that will be computedduring linting (⚠️ currently not implemented).
+
+### Example
+
+```owa
+(seq
+  ;; Define a function
+  (def greet (lambda [name]
+    (str.concat "Hello, " name "!")))
+
+  ;; Call it
+  (trace (greet "World")))
+```
+
+## Quick Start 🛠️
+
+### Requirements
+
+- Rust 1.70+ (for building from source)
+- Cargo
+
+### Build
+
+```bash
+git clone https://github.com/RuJect/owa-rs.git
+cd owa-rs
+cargo build --release
+```
+
+### Run a file
+
+```bash
+./target/release/owa-rs run hello.owa
+```
+
+### Run directly without owu
+
+```bash
+./target/release/owa-rs --no-owu hello.owa
+```
+
+### Flags
+
+When running via owu, these flags are available:
+
+- `--no-builtins`: skip Rust built-ins
+- `--no-core`: skip loading core library
+- `--no-std`: skip loading standard library
+- `--debug`: enable debug mode
+- `--test`: run in test mode
+
+## Architecture 🏗️
+
+OWA-RS follows a **Parse → Interpret** pipeline with modular design:
+
+### Rust core
+
+- `src/parser/`: source code → AST
+- `src/core/interpreter.rs`: evaluates AST nodes
+- `src/core/scope.rs`: manages variables and closures
+- `src/builtins/`: runtime primitives and host operations
+
+### Modular standard library
+
+- `modules/core/`: core language utilities, types, math, error handling, loops, tests
+- `modules/std/`: higher-level helpers such as `path` and `platform`
+- `modules/owu/`: command-line interface and `run` command support
+
+The runtime stays intentionally small, while higher-level language features live in library code.
+
+## Built-in API 🔧
+
+OWA-RS follows a **minimalist principle** for Rust built-ins: the runtime only implements fundamental primitives and avoids domain/application logic. The result is a small, focused runtime with powerful libraries built on top.
+
+### Core operations
+
+- Language: `def`, `lambda`, `macro`, `seq`, `trace`, `apply`, `lookup`, `include`
+- Scope: `scope`, `set!`, `unset!`, `exec`
+- Type inspection: `typeof`, `cmp`
+- Flow: `return`, `break`, `continue` (via `flow` namespace)
+- Errors: `throw`, `catch` (via `errors` namespace)
+
+### Built-in namespaces
+
+- `math`: arithmetic and numeric helpers
+- `str`: string construction and serialization
+- `vec`: vector creation and folding
+- `map`: maps and lookup
+- `set`: set operations
+- `cond`: conditional helpers like `if-eq` and `match`
+- `platform`: environment, CLI parsing, debug flags
+
+## Standard Library 📚
+
+The standard library is organized in modules:
+
+### Core Library (`modules/core/`)
+
+Essential functionality available by default when running through owu:
+
+- `assert.owa`: Assertion utilities for testing
+- `types/`: Type checking and predicates, including:
+  - `main.owa`: Core type utilities and predicates
+  - `bool.owa`, `str.owa`, `vec.owa`, `map.owa`, `set.owa`, `null.owa`, `option.owa`: Type-specific operations
+- `cmp.owa`: Comparison operations
+- `math.owa`: Arithmetic operations
+- `error.owa`: Error handling
+- `loop.owa`: Looping constructs
+- `test.owa`: Testing framework
+
+### Standard Library (`modules/std/`)
+
+Additional utilities:
+
+- `platform.owa`: Platform-specific operations
+
+### owu (`modules/owu/`)
+
+The OWA Utility tool:
+
+- `cli/`: Command-line interface framework
+- `cli/run.owa`: The `run` command handler
+
+## Performance ⚡
+
+OWA-RS is a tree-walking interpreter with reasonable performance for its simplicity. Rust's persistent data structures (via rpds) provide efficient immutable collections.
+
+For performance-critical workloads, consider:
+
+- Writing hot paths in Rust as built-ins
+- Avoiding deeply nested function calls
+- Using tail recursion where possible
+
+See `benchmarks/` for sample performance characteristics.
+
+## Examples 🌟
+
+### Hello World
+
+```owa
+(trace "Hello, OWA-RS!")
+```
+
+### Using Functions from Core
+
+```owa
+(def fib (lambda [n]
+  (if (>= n 2)
+    (+ (fib (- n 1)) (fib (- n 2)))
+    n)))
+
+(trace (fib 10))
+```
+
+Run with: `./target/release/owa-rs run fib.owa`
+
+### Working with Collections
+
+```owa
+(def numbers [1 2 3 4 5])
+(trace (vec.len numbers))
+(trace (vec.first numbers))
+
+(def config {:name "OWA" :version "0.1.0"})
+(trace (map.get config :name))
+```
+
+## Development 🛠️
+
+### Running Tests
+
+The core library has a built-in testing framework:
+
+```bash
+./target/release/owa-rs run --test modules/core/tests/main.owa
+```
+
+### Building Documentation
+
+To understand the codebase:
+
+- `src/core/interpreter.rs` - Main evaluation logic
+- `src/builtins/` - Rust built-in implementations
+- `modules/core/` - OWA standard library code
+- `modules/owu/cli/` - Command-line interface implementation
+
+## TODOs 📋
+
+### High Priority
+
+- [ ] Add proper error reporting with location information
+- [ ] Improve debugging/tracing utilities
+- [ ] Add REPL mode for interactive development
+- [ ] Implement tail call optimization
+
+### Medium Priority
+
+- [ ] Pattern matching enhancements
+- [x] Destructuring in set!/def
+- [ ] More comprehensive std library
+- [ ] Package manager / module repository
+- [ ] Performance profiling tools
+
+### Lower Priority
+
+- [ ] Concurrency support
+- [x] FFI (Foreign Function Interface)
+- [ ] File system operations (fs module)
+- [ ] Random number generation
+- [ ] Compilation to bytecode
+- [ ] Lint phase
+
+### Completed
+
+- [x] Annotations
+- [x] Separate core and std libraries
+- [x] CLI framework with commands
+- [x] Testing framework
+- [x] Error handling macros
+
+## Contributing 🤝
+
+This is a learning project exploring language design and implementation. Contributions are welcome!
+
+Areas where help is appreciated:
+
+- Standard library expansion
+- Bug fixes and optimizations
+- Documentation and examples
+- Testing and benchmarking
+
+## License 📄
+
+Unlicense License - see LICENSE file.
+
+---
+
+Made with ❤️ and lots of ☕ as a Rust learning project!
diff --git a/benchmarks/bench.ps1 b/benchmarks/bench.ps1
new file mode 100644
index 0000000..b8c4653
--- /dev/null
+++ b/benchmarks/bench.ps1
@@ -0,0 +1,17 @@
+$fileDirname = $PSScriptRoot
+$owaCmd = ".\target\release\owa-rs.exe"
+
+for ($i = 1; $i -le 1; $i++) {
+    $pythonFile = "$fileDirname/case$i/main.py"
+    $owaFile = "$fileDirname/case$i/main.owa"
+    $noOwuFile = "$fileDirname/case$i/no_owu.owa"
+    Write-Host "Running case #$i"
+    hyperfine `
+        --warmup 5 `
+        --min-runs 50 `
+        --show-output `
+        --export-markdown "$fileDirname/case$i/result.md" `
+        "python3.14 $pythonFile" `
+        "$owaCmd run $owaFile" `
+        "$owaCmd --no-owu $noOwuFile"
+}
diff --git a/benchmarks/bench.sh b/benchmarks/bench.sh
new file mode 100644
index 0000000..e736a62
--- /dev/null
+++ b/benchmarks/bench.sh
@@ -0,0 +1,18 @@
+#!/usr/bin/env sh
+file_dirname="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+owa_cmd="./target/release/owa-rs"
+
+for i in $(seq 1 1); do
+  python_file="${file_dirname}/case${i}/main.py"
+  owa_file="${file_dirname}/case${i}/main.owa"
+  no_owu_file="${file_dirname}/case${i}/no_owu.owa"
+  echo "Running case #${i}"
+  hyperfine \
+    --warmup 5 \
+    --min-runs 50 \
+    --show-output \
+    --export-markdown "${file_dirname}/case${i}/result.md" \
+    "python3 $python_file" \
+    "$owa_cmd run $owa_file" \
+    "$owa_cmd --no-owu $no_owu_file"
+done
\ No newline at end of file
diff --git a/benchmarks/case1/main.owa b/benchmarks/case1/main.owa
new file mode 100644
index 0000000..7106c31
--- /dev/null
+++ b/benchmarks/case1/main.owa
@@ -0,0 +1,8 @@
+(seq
+  (def fib (lambda [n]
+    (match n
+      (0 0)
+      (1 1)
+      (_ (+ (this (- n 1)) (this (- n 2)))))))
+  (trace (fib 12))
+)
\ No newline at end of file
diff --git a/benchmarks/case1/main.py b/benchmarks/case1/main.py
new file mode 100644
index 0000000..0cc8d2e
--- /dev/null
+++ b/benchmarks/case1/main.py
@@ -0,0 +1,9 @@
+def fib(n):
+    if n == 0:
+        return 0
+    if n == 1:
+        return 1
+    return fib(n - 1) + fib(n - 2)
+
+
+print(fib(12))
diff --git a/benchmarks/case1/no_owu.owa b/benchmarks/case1/no_owu.owa
new file mode 100644
index 0000000..fda9726
--- /dev/null
+++ b/benchmarks/case1/no_owu.owa
@@ -0,0 +1,8 @@
+(builtins.seq
+  (builtins.def fib (builtins.lambda [n]
+    (builtins.cond.match n
+      (0 0)
+      (1 1)
+      (_ (builtins.math.add (this (builtins.math.sub n 1)) (this (builtins.math.sub n 2)))))))
+  (builtins.trace (fib 12))
+)
\ No newline at end of file
diff --git a/benchmarks/case1/result.md b/benchmarks/case1/result.md
new file mode 100644
index 0000000..bb7373d
--- /dev/null
+++ b/benchmarks/case1/result.md
@@ -0,0 +1,5 @@
+| Command | Mean [ms] | Min [ms] | Max [ms] | Relative |
+|:---|---:|---:|---:|---:|
+| `python3.14 D:\Tools\Projects\owa-rs\benchmarks/case1/main.py` | 40.5 ± 0.7 | 39.5 | 43.1 | 2.38 ± 0.36 |
+| `.\target\release\owa-rs.exe run D:\Tools\Projects\owa-rs\benchmarks/case1/main.owa` | 53.3 ± 1.2 | 51.5 | 57.6 | 3.14 ± 0.48 |
+| `.\target\release\owa-rs.exe --no-owu D:\Tools\Projects\owa-rs\benchmarks/case1/no_owu.owa` | 17.0 ± 2.6 | 15.3 | 37.5 | 1.00 |
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..012fb16
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,175 @@
+{
+  "nodes": {
+    "fenix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src"
+      },
+      "locked": {
+        "lastModified": 1776497206,
+        "narHash": "sha256-Em+RSdFnwyyKPGUBFtQYtVjm+1UvIc9gOR91Y22zlzg=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "df2295365fb081fe0745449762a771290782c22d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
+    "fenix_2": {
+      "inputs": {
+        "nixpkgs": [
+          "naersk",
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src_2"
+      },
+      "locked": {
+        "lastModified": 1752475459,
+        "narHash": "sha256-z6QEu4ZFuHiqdOPbYss4/Q8B0BFhacR8ts6jO/F/aOU=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "bf0d6f70f4c9a9cf8845f992105652173f4b617f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "naersk": {
+      "inputs": {
+        "fenix": "fenix_2",
+        "nixpkgs": "nixpkgs"
+      },
+      "locked": {
+        "lastModified": 1776200608,
+        "narHash": "sha256-broZ6RFQr4Fv0wT73gGmzNX14A43TmTFF8g4wDKlNss=",
+        "owner": "nix-community",
+        "repo": "naersk",
+        "rev": "8b23250ab45c2a38cd91031aee26478ca4d0a28e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "naersk",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1752077645,
+        "narHash": "sha256-HM791ZQtXV93xtCY+ZxG1REzhQenSQO020cu6rHtAPk=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "be9e214982e20b8310878ac2baa063a961c1bdf6",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1776169885,
+        "narHash": "sha256-l/iNYDZ4bGOAFQY2q8y5OAfBBtrDAaPuRQqWaFHVRXM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "4bd9165a9165d7b5e33ae57f3eecbcb28fb231c9",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "fenix": "fenix",
+        "flake-utils": "flake-utils",
+        "naersk": "naersk",
+        "nixpkgs": "nixpkgs_2"
+      }
+    },
+    "rust-analyzer-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1776441750,
+        "narHash": "sha256-1rVfG+mj8R4ze+lSYCa4iAv7FzrB03Cprtxmd1MfZak=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "251df518d73abb5c5d573c4d5d266a3edae9ca5a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
+      }
+    },
+    "rust-analyzer-src_2": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1752428706,
+        "narHash": "sha256-EJcdxw3aXfP8Ex1Nm3s0awyH9egQvB2Gu+QEnJn2Sfg=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "591e3b7624be97e4443ea7b5542c191311aa141d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..0240bb6
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,48 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    fenix = {
+      url = "github:nix-community/fenix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    flake-utils.url = "github:numtide/flake-utils";
+    naersk.url = "github:nix-community/naersk";
+  };
+
+  outputs = {
+    nixpkgs,
+    fenix,
+    flake-utils,
+    naersk,
+    ...
+  }:
+    flake-utils.lib.eachDefaultSystem (
+      system: let
+        pkgs = (import nixpkgs) {
+          inherit system;
+          overlays = [fenix.overlays.default];
+        };
+        naersk' = pkgs.callPackage naersk {};
+      in {
+        defaultPackage = naersk'.buildPackage {
+          src = ./.;
+        };
+
+        devShell = pkgs.mkShell {
+          nativeBuildInputs = with pkgs; [
+            hyperfine
+            python3
+            alejandra
+            rust-analyzer
+            (pkgs.fenix.stable.withComponents [
+              "cargo"
+              "clippy"
+              "rust-src"
+              "rustc"
+              "rustfmt"
+            ])
+          ];
+        };
+      }
+    );
+}
diff --git a/modules/core/assert.owa b/modules/core/assert.owa
new file mode 100644
index 0000000..2cd641e
--- /dev/null
+++ b/modules/core/assert.owa
@@ -0,0 +1,17 @@
+(namespace assert
+  (defmacro ok! [] (if (bool.and $%&)
+    :true
+    (throw! "assertion failed")))
+
+  (defmacro not! [] (if (bool.and $%&)
+    (throw! "assertion failed")
+    :true))
+
+  (defmacro eq! [] (if-eq $(%&)
+    :true
+    (throw! "assertion failed")))
+
+  (defmacro nq! [] (if-eq $(%&)
+    (throw! "assertion failed")
+    :true))
+)
\ No newline at end of file
diff --git a/modules/core/ast.owa b/modules/core/ast.owa
new file mode 100644
index 0000000..e72ad3d
--- /dev/null
+++ b/modules/core/ast.owa
@@ -0,0 +1,10 @@
+(namespace ast
+  (defmacro pack! [v]
+    (builtins.ast.pack $v))
+
+  (defmacro value! [v]
+    (map.get (ast.pack! $v) :data))
+
+  (defmacro type! [v]
+    (map.get (ast.pack! $v) :type))
+)
\ No newline at end of file
diff --git a/modules/core/branch.owa b/modules/core/branch.owa
new file mode 100644
index 0000000..e37a141
--- /dev/null
+++ b/modules/core/branch.owa
@@ -0,0 +1,12 @@
+(seq
+  ;; builtins
+  (def if-eq builtins.cond.if_eq)
+  (def match builtins.cond.match)
+  (def if-has builtins.cond.if_has)
+  
+  (defmacro if [cond then]
+    (if-eq (:false $cond) (seq $%&) (seq $then)))
+
+  (defmacro unless [cond then]
+    (if-eq (:false $cond) (seq $then) (seq $%&)))
+)
\ No newline at end of file
diff --git a/modules/core/cmp.owa b/modules/core/cmp.owa
new file mode 100644
index 0000000..a1b99a8
--- /dev/null
+++ b/modules/core/cmp.owa
@@ -0,0 +1,25 @@
+(seq
+  (defmacro eq? <Bool>[]
+    (if-eq ($%%) :true :false))
+  (defmacro nq? <Bool>[]
+    (if-eq ($%%) :false :true))
+
+  (fn cmp <Keyword>[left right]
+    (match (builtins.cmp left right)
+      (-1 :less)
+      (0 :equal)
+      (1 :greater)))
+
+
+  (fn lt? <Bool>[left right]
+    (eq? (cmp left right) :less))
+
+  (fn lte? <Bool>[left right]
+    (bool.or (lt? left right) (eq? left right)))
+
+  (fn gt? <Bool>[left right]
+    (eq? (cmp left right) :greater))
+
+  (fn gte? <Bool>[left right]
+    (bool.or (gt? left right) (eq? left right)))
+)
\ No newline at end of file
diff --git a/modules/core/error.owa b/modules/core/error.owa
new file mode 100644
index 0000000..c9dddd4
--- /dev/null
+++ b/modules/core/error.owa
@@ -0,0 +1,22 @@
+(seq
+  (fn throw! []
+    (throw.runtime_error! (str.join "" %%)))
+  (fn panic! [v]
+    (throw.panic! v))
+  (fn unreachable! []
+    (throw! "Reached unreachable code"))
+  (fn not_implemented! []
+    (throw! "Not implemented"))
+  (def try builtins.errors.try)
+
+  (defmacro catch [pattern then]
+    (lambda [msg type] (if-eq (type $pattern)
+      $then
+      :null)))
+
+  (namespace throw
+    (def panic! builtins.errors.throw_panic)
+    (def type_error! builtins.errors.throw_type_error)
+    (def arity_error! builtins.errors.throw_arity_error)
+    (def runtime_error! builtins.errors.throw_runtime_error)
+  ))
\ No newline at end of file
diff --git a/modules/core/ffi.owa b/modules/core/ffi.owa
new file mode 100644
index 0000000..563644f
--- /dev/null
+++ b/modules/core/ffi.owa
@@ -0,0 +1,32 @@
+(namespace ffi
+    (def unload builtins.ffi.unload)
+
+    (def ctypes [
+        :i8 :i16 :i32 :i64
+        :u8 :u16 :u32 :u64
+        :f32 :f64
+        :ptr
+        :str
+    ])
+
+    (defmacro extern [name libname]
+        (namespace $name
+            (builtins.ffi.load $libname)
+            (fn call [symbol signature args]
+                (builtins.ffi.call $libname symbol signature args)
+            )
+        )
+    )
+
+    (defmacro native [name libname]
+        (namespace $name
+            (builtins.ffi.load $libname)
+            (defmacro fn [name symbol args ret]
+                (def '$name #(builtins.ffi.call $libname '$symbol ['$args '$ret] %&))
+            )
+            $%&
+        )
+    )
+
+    (extern ucrtbase "ucrtbase.dll")
+)
diff --git a/modules/core/lambda.owa b/modules/core/lambda.owa
new file mode 100644
index 0000000..d25023a
--- /dev/null
+++ b/modules/core/lambda.owa
@@ -0,0 +1,8 @@
+(seq
+  ;; builtins
+  (def apply builtins.apply)
+  (def lambda builtins.lambda)
+
+  (defmacro fn [name params body]
+    (def $name (lambda $params $body)))
+)
\ No newline at end of file
diff --git a/modules/core/loop.owa b/modules/core/loop.owa
new file mode 100644
index 0000000..62b0251
--- /dev/null
+++ b/modules/core/loop.owa
@@ -0,0 +1,23 @@
+(seq
+  (def break builtins.flow.break)
+  (def continue builtins.flow.continue)
+  (def loop builtins.flow.loop)
+
+  (defmacro return []
+    (builtins.flow.return $%% null))
+
+  (defmacro while [cond] (loop
+    (if (eq? $cond :false) (break) :null)
+    $%&))
+
+  (defmacro do-while [cond] (loop
+    $%&
+    (if (eq? $cond :false) (break) :null)))
+
+  (defmacro for [var iter] (vec.map
+    (lambda [x] (seq
+      (def $var x)
+      $%&))
+    (vec.from $iter)
+  ))
+)
diff --git a/modules/core/main.owa b/modules/core/main.owa
new file mode 100644
index 0000000..fd68654
--- /dev/null
+++ b/modules/core/main.owa
@@ -0,0 +1,25 @@
+(builtins.seq
+  (builtins.def include builtins.include)
+
+  (include "scope")
+  (include "branch")
+  (include "lambda")
+
+  (def exec builtins.exec)
+  (def trace builtins.trace)
+  (def typeof builtins.typeof)
+
+  (fn identity [x] x)
+
+  (include "types")
+  (include "assert")
+  (include "ast")
+  (include "cmp")
+  (include "error")
+  (include "ffi")
+  (include "loop")
+  (include "math")
+  (include "test")
+
+  (test.space "core" (include "tests/main"))
+)
diff --git a/modules/core/math.owa b/modules/core/math.owa
new file mode 100644
index 0000000..7d045de
--- /dev/null
+++ b/modules/core/math.owa
@@ -0,0 +1,14 @@
+(seq
+  (def + builtins.math.add)
+  (def - builtins.math.sub)
+  (def * builtins.math.mul)
+  (def / builtins.math.div)
+  (def % builtins.math.mod)
+  (def ** builtins.math.pow)
+
+  (fn ++ <Number>[<Number>x]
+    (+ x 1))
+
+  (fn -- <Number>[<Number>x]
+    (- x 1))
+)
\ No newline at end of file
diff --git a/modules/core/scope.owa b/modules/core/scope.owa
new file mode 100644
index 0000000..e4945e0
--- /dev/null
+++ b/modules/core/scope.owa
@@ -0,0 +1,22 @@
+(builtins.seq
+  ;; builtins
+  (builtins.def def builtins.def)
+  (def lookup builtins.lookup)
+  (def set! builtins.set!)
+  (def scope builtins.scope)
+  
+  ;; macro
+  (def macro builtins.macro)
+  (def defmacro (macro [name params body]
+    (def $name (macro $params $body))))
+
+  ;; flow
+  (defmacro seq []
+    (builtins.seq :null $%&))
+  (defmacro namespace [name] (def $name (scope $%&)))
+
+  ;; other
+  (defmacro mut! [v fn] (seq
+    (set! (ast.value! $v) ($fn $v $%&)))
+  )
+)
\ No newline at end of file
diff --git a/modules/core/test.owa b/modules/core/test.owa
new file mode 100644
index 0000000..af392d7
--- /dev/null
+++ b/modules/core/test.owa
@@ -0,0 +1,16 @@
+(namespace test
+  (def target (lookup __test__ null))
+
+  (defmacro if-target [then]
+    (if-eq (test.target null) :null (seq $%%)))
+
+  (defmacro case [name] (test.if-target
+    (builtins.errors.try
+      (scope $%& (trace "Running test \"" $name "\": OK ✅"))
+      #(trace "Running test \"" $name "\": FAILED ❌ (" %2 ": " %1 ")"))))
+
+  (defmacro space [name] (if
+    (bool.or (eq? test.target $name) (eq? test.target "."))
+    (namespace $name (seq $%&))
+  ))
+)
\ No newline at end of file
diff --git a/modules/core/tests/bool.owa b/modules/core/tests/bool.owa
new file mode 100644
index 0000000..28053f8
--- /dev/null
+++ b/modules/core/tests/bool.owa
@@ -0,0 +1,38 @@
+(namespace tests.bool
+  (test.case "bool.bool?"
+    (assert.ok! (bool? true))
+    (assert.ok! (bool? false))
+    (assert.not! (bool? 1))
+  )
+
+  (test.case "bool.not"
+    (assert.eq! (bool.not true) false)
+    (assert.eq! (bool.not false) true)
+  )
+
+  (test.case "bool.and"
+    (assert.ok! (bool.and true true))
+    (assert.not! (bool.and true false))
+    (assert.not! (bool.and false true))
+    (assert.not! (bool.and false false))
+  )
+
+  (test.case "bool.or"
+    (assert.ok! (bool.or true true))
+    (assert.ok! (bool.or true false))
+    (assert.ok! (bool.or false true))
+    (assert.not! (bool.or false false))
+  )
+
+  (test.case "bool.nand"
+    (assert.not! (bool.nand true true))
+    (assert.ok! (bool.nand true false))
+    (assert.ok! (bool.nand false true))
+    (assert.ok! (bool.nand false false))
+  )
+
+  (test.case "bool.new"
+    (assert.eq! (bool.new true) true)
+    (assert.eq! (bool.new false) false)
+  )
+)
diff --git a/modules/core/tests/cmp.owa b/modules/core/tests/cmp.owa
new file mode 100644
index 0000000..02dc157
--- /dev/null
+++ b/modules/core/tests/cmp.owa
@@ -0,0 +1,41 @@
+(namespace tests.cmp
+  (test.case "cmp.eq?"
+    (assert.ok! (eq? 1 1))
+    (assert.not! (eq? 1 2))
+  )
+
+  (test.case "cmp.nq?"
+    (assert.ok! (nq? 1 2))
+    (assert.not! (nq? 1 1))
+  )
+
+  (test.case "cmp.cmp"
+    (assert.eq! (cmp 1 2) :less)
+    (assert.eq! (cmp 2 1) :greater)
+    (assert.eq! (cmp 1 1) :equal)
+  )
+
+  (test.case "cmp.lt?"
+    (assert.ok! (lt? 1 2))
+    (assert.not! (lt? 2 1))
+    (assert.not! (lt? 1 1))
+  )
+
+  (test.case "cmp.lte?"
+    (assert.ok! (lte? 1 2))
+    (assert.ok! (lte? 1 1))
+    (assert.not! (lte? 2 1))
+  )
+
+  (test.case "cmp.gt?"
+    (assert.ok! (gt? 2 1))
+    (assert.not! (gt? 1 2))
+    (assert.not! (gt? 1 1))
+  )
+
+  (test.case "cmp.gte?"
+    (assert.ok! (gte? 2 1))
+    (assert.ok! (gte? 1 1))
+    (assert.not! (gte? 1 2))
+  )
+)
diff --git a/modules/core/tests/loop.owa b/modules/core/tests/loop.owa
new file mode 100644
index 0000000..d8732b1
--- /dev/null
+++ b/modules/core/tests/loop.owa
@@ -0,0 +1,42 @@
+(namespace tests.loop
+  (test.case "while.basic-true"
+    (def counter 0)
+    (while (eq? counter 0)
+      (set! counter 1))
+    (assert.eq! counter 1)
+  )
+
+  (test.case "while.condition-false"
+    (def counter 5)
+    (while (lt? counter 0)
+      (set! counter (+ counter 1)))
+    (assert.eq! counter 5)
+  )
+
+  (test.case "while.counting-loop"
+    (def n 0)
+    (while (lt? n 10)
+      (set! n (+ n 1)))
+    (assert.eq! n 10)
+  )
+
+  (test.case "while.loop-condition-reached"
+    (def i 0)
+    (while (lt? i 5)
+      (set! i (+ i 1)))
+    (assert.eq! i 5)
+  )
+
+  (test.case "while.nested"
+    (def outer 0)
+    (def inner 0)
+    (def total 0)
+    (while (lt? outer 3)
+      (set! inner 0)
+      (while (lt? inner 2)
+        (set! total (+ total 1))
+        (set! inner (+ inner 1)))
+      (set! outer (+ outer 1)))
+    (assert.eq! total 6)
+  )
+)
diff --git a/modules/core/tests/main.owa b/modules/core/tests/main.owa
new file mode 100644
index 0000000..93984f4
--- /dev/null
+++ b/modules/core/tests/main.owa
@@ -0,0 +1,14 @@
+(seq
+  (include "vec")
+  (include "str")
+  (include "set")
+  (include "map")
+  (include "bool")
+  (include "option")
+  (include "scope")
+  (include "null")
+  (include "cmp")
+  (include "math")
+  (include "types")
+  (include "loop")
+)
diff --git a/modules/core/tests/map.owa b/modules/core/tests/map.owa
new file mode 100644
index 0000000..7b267dc
--- /dev/null
+++ b/modules/core/tests/map.owa
@@ -0,0 +1,83 @@
+(namespace tests.map
+  (test.case "map.len"
+    (assert.eq! (map.len (map.new)) 0)
+  )
+
+  (test.case "map.empty?"
+    (assert.ok! (map.empty? (map.new)))
+  )
+
+  (test.case "map.is-empty?"
+    (assert.ok! (map.is-empty? (map.new)))
+  )
+
+  (test.case "map.get"
+    (seq
+      (def m (map.new :a 1 :b 2))
+      (assert.eq! (map.get m :a) 1)
+      (assert.eq! (map.get m :b) 2)
+      (assert.eq! (map.get m :c) null)
+    )
+  )
+
+  (test.case "map.put"
+    (seq
+      (def m (map.new :a 1))
+      (def m2 (map.put m :b 2))
+      (assert.eq! (map.len m2) 2)
+      (assert.eq! (map.get m2 :b) 2)
+    )
+  )
+
+  (test.case "map.has-key?"
+    (seq
+      (def m (map.new :a 1 :b 2))
+      (assert.ok! (map.has-key? m :a))
+      (assert.not! (map.has-key? m :c))
+    )
+  )
+
+  (test.case "map.has-value?"
+    (seq
+      (def m (map.new :a 1 :b 2))
+      (assert.ok! (map.has-value? m 1))
+      (assert.not! (map.has-value? m 5))
+    )
+  )
+
+  (test.case "map.keys"
+    (seq
+      (def m (map.new :a 1 :b 2))
+      (def ks (map.keys m))
+      (assert.eq! (vec.len ks) 2)
+    )
+  )
+
+  (test.case "map.values"
+    (seq
+      (def m (map.new :a 1 :b 2))
+      (def vs (map.values m))
+      (assert.eq! (vec.len vs) 2)
+    )
+  )
+
+  (test.case "map.merge"
+    (seq
+      (def m1 (map.new :a 1 :b 2))
+      (def m2 (map.new :b 20 :c 3))
+      (def m3 (map.merge m1 m2))
+      (assert.eq! (map.get m3 :a) 1)
+      (assert.eq! (map.get m3 :b) 20)
+      (assert.eq! (map.get m3 :c) 3)
+    )
+  )
+
+  (test.case "map.dissoc"
+    (seq
+      (def m (map.new :a 1 :b 2 :c 3))
+      (def m2 (map.dissoc m :b))
+      (assert.eq! (map.len m2) 2)
+      (assert.not! (map.has-key? m2 :b))
+    )
+  )
+)
diff --git a/modules/core/tests/math.owa b/modules/core/tests/math.owa
new file mode 100644
index 0000000..176e564
--- /dev/null
+++ b/modules/core/tests/math.owa
@@ -0,0 +1,40 @@
+(namespace tests.math
+  (test.case "math.add"
+    (assert.eq! (+ 1 2) 3)
+    (assert.eq! (+ 0 0) 0)
+  )
+
+  (test.case "math.sub"
+    (assert.eq! (- 5 3) 2)
+    (assert.eq! (- 1 1) 0)
+  )
+
+  (test.case "math.mul"
+    (assert.eq! (* 3 4) 12)
+    (assert.eq! (* 0 5) 0)
+  )
+
+  (test.case "math.div"
+    (assert.eq! (/ 10 2) 5)
+  )
+
+  (test.case "math.mod"
+    (assert.eq! (% 10 3) 1)
+    (assert.eq! (% 5 5) 0)
+  )
+
+  (test.case "math.pow"
+    (assert.eq! (** 2 3) 8)
+    (assert.eq! (** 5 2) 25)
+  )
+
+  (test.case "math.++"
+    (assert.eq! (++ 5) 6)
+    (assert.eq! (++ 0) 1)
+  )
+
+  (test.case "math.--"
+    (assert.eq! (-- 5) 4)
+    (assert.eq! (-- 0) -1)
+  )
+)
diff --git a/modules/core/tests/null.owa b/modules/core/tests/null.owa
new file mode 100644
index 0000000..a2b9d5b
--- /dev/null
+++ b/modules/core/tests/null.owa
@@ -0,0 +1,8 @@
+(namespace tests.null
+  (test.case "null.null?"
+    (assert.ok! (null? null))
+    (assert.ok! (null? :nil))
+    (assert.not! (null? 0))
+    (assert.not! (null? false))
+  )
+)
diff --git a/modules/core/tests/option.owa b/modules/core/tests/option.owa
new file mode 100644
index 0000000..7bd52f8
--- /dev/null
+++ b/modules/core/tests/option.owa
@@ -0,0 +1,33 @@
+(namespace tests.option
+  (test.case "option.ok"
+    (seq
+      (def opt (option.ok 42))
+      (assert.ok! (option.ok? opt))
+      (assert.eq! (vec.get opt 1) 42)
+    )
+  )
+
+  (test.case "option.err"
+    (seq
+      (def opt (option.err "error"))
+      (assert.ok! (option.err? opt))
+      (assert.eq! (vec.get opt 1) "error")
+    )
+  )
+
+  (test.case "option.ok?"
+    (assert.ok! (option.ok? (option.ok 1)))
+    (assert.not! (option.ok? (option.err "x")))
+  )
+
+  (test.case "option.err?"
+    (assert.ok! (option.err? (option.err "x")))
+    (assert.not! (option.err? (option.ok 1)))
+  )
+
+  (test.case "option.option?"
+    (assert.ok! (option? (option.ok 1)))
+    (assert.ok! (option? (option.err "x")))
+    (assert.not! (option? [1 2]))
+  )
+)
diff --git a/modules/core/tests/scope.owa b/modules/core/tests/scope.owa
new file mode 100644
index 0000000..2f36890
--- /dev/null
+++ b/modules/core/tests/scope.owa
@@ -0,0 +1,78 @@
+(namespace tests.scopes
+  (test.case "def"
+    (def x 1)
+    (assert.eq! x 1)
+
+    (def [y z] [1 2])
+    (assert.eq! y 1)
+    (assert.eq! z 2)
+  )
+
+  (test.case "def bounded"
+    (def x 1)
+    (try
+      (def x 2)
+      (catch :Panic (return))
+    )
+    (unreachable!)
+  )
+
+  (test.case "set!"
+    (def [x y] [1 1])
+    (set! x 2)
+    (assert.eq! x 2)
+
+    (set! [x y] [3 4])
+    (assert.eq! x 3)
+    (assert.eq! y 4)
+  )
+
+  (test.case "set! unbounded"
+    (try
+      (set! x 2)
+      (catch :UnboundVariable (return))
+    )
+    (unreachable!)
+  )
+
+  (test.case "lookup"
+    (def x 1)
+    (assert.eq! (lookup x null) 1)
+    (assert.eq! (lookup y null) null)
+  )
+
+  (test.case "inheritance"
+    (scope
+      (def x 1)
+      (scope
+        (assert.eq! x 1)
+        (set! x 2)
+      )
+      (assert.eq! x 2)
+    )
+  )
+
+  (test.case "shadowing"
+    (scope
+      (def x 100)
+      (scope
+        (def x 1)
+      )
+      (assert.eq! x 100)
+    )
+    (assert.eq! (lookup x null) null)
+  )
+
+  (test.case "leakage"
+    (scope (def x 1))
+    (assert.eq! (lookup x null) null)
+
+    (scope (def y 2))
+    (assert.eq! (lookup y null) null)
+
+    (scope
+      (scope (def z 1))
+      (assert.eq! (lookup z null) null)
+    )
+  )
+)
diff --git a/modules/core/tests/set.owa b/modules/core/tests/set.owa
new file mode 100644
index 0000000..440f991
--- /dev/null
+++ b/modules/core/tests/set.owa
@@ -0,0 +1,44 @@
+(namespace tests.set
+  (test.case "set.empty?"
+    (assert.ok! (set.empty? (set.new)))
+    (assert.not! (set.empty? (set.new 1)))
+  )
+
+  (test.case "set.len"
+    (assert.eq! (set.len (set.new)) 0)
+    (assert.eq! (set.len (set.new 1)) 1)
+    (assert.eq! (set.len (set.new 1 2 3)) 3)
+  )
+
+  (test.case "set.has"
+    (assert.ok! (set.has (set.new 1 2 3) 2))
+    (assert.not! (set.has (set.new 1 2 3) 5))
+  )
+
+  (test.case "set.add"
+    (assert.ok! (set.has (set.add (set.new 1 2) 3) 3))
+    (assert.eq! (set.len (set.add (set.new 1 2) 3)) 3)
+  )
+
+  (test.case "set.remove"
+    (assert.not! (set.has (set.remove (set.new 1 2 3) 2) 2))
+    (assert.eq! (set.len (set.remove (set.new 1 2 3) 2)) 2)
+  )
+
+  (test.case "set.union"
+    (assert.eq! (set.len (set.union (set.new 1 2) (set.new 2 3))) 3)
+    (assert.ok! (set.has (set.union (set.new 1 2) (set.new 2 3)) 1))
+    (assert.ok! (set.has (set.union (set.new 1 2) (set.new 2 3)) 3))
+  )
+
+  (test.case "set.intersection"
+    (assert.eq! (set.len (set.intersection (set.new 1 2 3) (set.new 2 3 4))) 2)
+    (assert.ok! (set.has (set.intersection (set.new 1 2 3) (set.new 2 3 4)) 2))
+    (assert.ok! (set.has (set.intersection (set.new 1 2 3) (set.new 2 3 4)) 3))
+  )
+
+  (test.case "set.difference"
+    (assert.eq! (set.len (set.difference (set.new 1 2 3) (set.new 2 3))) 1)
+    (assert.ok! (set.has (set.difference (set.new 1 2 3) (set.new 2 3)) 1))
+  )
+)
\ No newline at end of file
diff --git a/modules/core/tests/str.owa b/modules/core/tests/str.owa
new file mode 100644
index 0000000..7388a99
--- /dev/null
+++ b/modules/core/tests/str.owa
@@ -0,0 +1,67 @@
+(namespace tests.str
+  (test.case "str.len"
+    (assert.eq! (str.len "") 0)
+    (assert.eq! (str.len "hello") 5)
+  )
+
+  (test.case "str.empty?"
+    (assert.ok! (str.empty? ""))
+    (assert.not! (str.empty? "a"))
+  )
+
+  (test.case "str.is-empty?"
+    (assert.ok! (str.is-empty? ""))
+    (assert.not! (str.is-empty? "a"))
+  )
+
+  (test.case "str.first"
+    (assert.eq! (str.first "hello") "h")
+  )
+
+  (test.case "str.last"
+    (assert.eq! (str.last "hello") "o")
+  )
+
+  (test.case "str.concat"
+    (assert.eq! (str.concat "hello" " " "world") "hello world")
+  )
+
+  (test.case "str.substring"
+    (assert.eq! (str.substring "hello" 0 3) "hel")
+    (assert.eq! (str.substring "hello" 1 4) "ell")
+  )
+
+  (test.case "str.take"
+    (assert.eq! (str.take "hello" 3) "hel")
+  )
+
+  (test.case "str.drop"
+    (assert.eq! (str.drop "hello" 2) "llo")
+  )
+
+  (test.case "str.reverse"
+    (assert.eq! (str.reverse "hello") "olleh")
+  )
+
+  (test.case "str.starts-with?"
+    (assert.ok! (str.starts-with? "hello" "hel"))
+    (assert.not! (str.starts-with? "hello" "xyz"))
+  )
+
+  (test.case "str.ends-with?"
+    (assert.ok! (str.ends-with? "hello" "lo"))
+    (assert.not! (str.ends-with? "hello" "xyz"))
+  )
+
+  (test.case "str.split"
+    (assert.eq! (str.split "hello world" " ") ["hello" "world"])
+    (assert.eq! (str.split "hello world" "w") ["hello " "orld"])
+    (assert.eq! (str.split "hello world" "x") ["hello world"])
+  )
+
+  (test.case "str.join"
+    (assert.eq! (str.join " " ["hello" "world"]) "hello world")
+    (assert.eq! (str.join "w" ["hello " "orld"]) "hello world")
+    (assert.eq! (str.join "x" ["hello world"]) "hello world")
+  )
+)
diff --git a/modules/core/tests/types.owa b/modules/core/tests/types.owa
new file mode 100644
index 0000000..9142923
--- /dev/null
+++ b/modules/core/tests/types.owa
@@ -0,0 +1,53 @@
+(namespace tests.types
+  (test.case "types.is?"
+    (assert.ok! (is? 42 :int))
+    (assert.ok! (is? "hello" :str))
+    (assert.ok! (is? [] :vec))
+    (assert.not! (is? 42 :str))
+  )
+
+  (test.case "types.guard"
+    (seq
+      (def int-guard (guard :int))
+      (assert.ok! (int-guard 42))
+      (assert.not! (int-guard "42"))
+    )
+  )
+
+  (test.case "types.kw?"
+    (assert.ok! (kw? :keyword))
+    (assert.not! (kw? "not-keyword"))
+  )
+
+  (test.case "types.type?"
+    (assert.ok! (type? :int))
+    (assert.ok! (type? :str))
+    (assert.not! (type? :unknown))
+  )
+
+  (test.case "types.str?"
+    (assert.ok! (str? "hello"))
+    (assert.not! (str? 42))
+  )
+
+  (test.case "types.vec?"
+    (assert.ok! (vec? []))
+    (assert.ok! (vec? [1 2 3]))
+    (assert.not! (vec? 42))
+  )
+
+  (test.case "types.bool?"
+    (assert.ok! (bool? true))
+    (assert.ok! (bool? false))
+    (assert.not! (bool? 1))
+  )
+
+  (test.case "types.null?"
+    (assert.ok! (null? null))
+    (assert.not! (null? 0))
+  )
+
+  (test.case "types.map.is?"
+    (assert.ok! (map.is? (map.new)))
+  )
+)
diff --git a/modules/core/tests/vec.owa b/modules/core/tests/vec.owa
new file mode 100644
index 0000000..28e31c4
--- /dev/null
+++ b/modules/core/tests/vec.owa
@@ -0,0 +1,91 @@
+(namespace tests.vec
+  (test.case "vec.empty?" 
+    (assert.ok! (vec.empty? []))
+    (assert.not! (vec.empty? [1]))
+  )
+
+  (test.case "vec.len"
+    (assert.eq! (vec.len []) 0)
+    (assert.eq! (vec.len [1]) 1)
+    (assert.eq! (vec.len [1 2 3]) 3)
+  )
+
+  (test.case "vec.first"
+    (assert.eq! (vec.first [1 2 3]) 1)
+    (assert.eq! (vec.first ["a"]) "a")
+  )
+
+  (test.case "vec.last"
+    (assert.eq! (vec.last [1 2 3]) 3)
+    (assert.eq! (vec.last ["x"]) "x")
+  )
+
+  (test.case "vec.get"
+    (assert.eq! (vec.get [10 20 30] 0) 10)
+    (assert.eq! (vec.get [10 20 30] 1) 20)
+    (assert.eq! (vec.get [10 20 30] 2) 30)
+  )
+
+  (test.case "vec.map"
+    (assert.eq! 
+      (vec.map (lambda [x _] (+ x 1)) [1 2 3])
+      [2 3 4])
+  )
+
+  (test.case "vec.filter"
+    (assert.eq!
+      (vec.filter (lambda [x _] (gt? x 1)) [1 2 3])
+      [2 3])
+  )
+
+  (test.case "vec.has"
+    (assert.ok! (vec.has [1 2 3] 2))
+    (assert.not! (vec.has [1 2 3] 5))
+  )
+
+  (test.case "vec.includes?"
+    (assert.ok! (vec.includes? [1 2 3] 2))
+    (assert.not! (vec.includes? [1 2 3] 5))
+  )
+
+  (test.case "vec.find"
+    (assert.eq! 
+      (vec.find (lambda [x _] (gt? x 2)) [1 2 3 4])
+      3)
+  )
+
+  (test.case "vec.reverse"
+    (assert.eq! (vec.reverse [1 2 3]) [3 2 1])
+  )
+
+  (test.case "vec.take"
+    (assert.eq! (vec.take [1 2 3 4 5] 3) [1 2 3])
+  )
+
+  (test.case "vec.drop"
+    (assert.eq! (vec.drop [1 2 3 4 5] 2) [3 4 5])
+  )
+
+  (test.case "vec.uniq"
+    (assert.eq! (vec.uniq [1 2 2 3 3 3]) [1 2 3])
+  )
+
+  (test.case "vec.every?"
+    (assert.ok! (vec.every? (lambda [x _] (gt? x 0)) [1 2 3]))
+    (assert.not! (vec.every? (lambda [x _] (gt? x 1)) [1 2 3]))
+  )
+
+  (test.case "vec.some?"
+    (assert.ok! (vec.some? (lambda [x _] (gt? x 2)) [1 2 3]))
+    (assert.not! (vec.some? (lambda [x _] (gt? x 5)) [1 2 3]))
+  )
+
+  (test.case "vec.count"
+    (assert.eq! (vec.count (lambda [x _] (gt? x 1)) [1 2 3]) 2)
+  )
+
+  (test.case "vec.sum"
+    (assert.eq! (vec.sum [1 2 3]) 6)
+    (assert.eq! (vec.sum []) 0)
+  )
+)
diff --git a/modules/core/types/bool.owa b/modules/core/types/bool.owa
new file mode 100644
index 0000000..94a88a0
--- /dev/null
+++ b/modules/core/types/bool.owa
@@ -0,0 +1,23 @@
+(seq
+  (def true :true)
+  (def false :false)
+  (fn bool? [x]
+    (bool.or (eq? x true) (eq? x false)))
+
+  (namespace bool
+    (fn new [x]
+      (eq? x true))
+    (def __call__ new)
+
+    (defmacro or []
+      (if-eq (false $%%) false true))
+
+    (defmacro and []
+      (if-has false ($%%) false true))
+
+    (defmacro nand []
+      (if-has false ($%%) true false))
+
+    (fn not [x]
+      (if-eq (x true) false true))
+  ))
diff --git a/modules/core/types/main.owa b/modules/core/types/main.owa
new file mode 100644
index 0000000..0e3b226
--- /dev/null
+++ b/modules/core/types/main.owa
@@ -0,0 +1,39 @@
+(seq
+  (def types [
+    :symbol
+    :keyword
+    :str
+    :float
+    :int
+    :vec
+    :call
+    :set
+    :map
+    :quote
+    :lambda
+    :macro
+  ])
+
+  (fn is? [x type]
+    (eq? (typeof x) type))
+  (fn guard [type]
+    (lambda [x] (is? x type)))
+
+  (def kw? (guard :keyword))
+  (def kw builtins.str.kw)
+
+  (include "bool")
+  (include "map")
+  (include "null")
+  (include "option")
+  (include "set")
+  (include "str")
+  (include "struct")
+  (include "vec")
+
+  (def vec? (guard :vec))
+  (def map? (guard :map))
+
+  (fn type? [x]
+    (vec.has types x))
+)
\ No newline at end of file
diff --git a/modules/core/types/map.owa b/modules/core/types/map.owa
new file mode 100644
index 0000000..8792960
--- /dev/null
+++ b/modules/core/types/map.owa
@@ -0,0 +1,94 @@
+(namespace map
+  (def type :map)
+  (def is? (guard type))
+  (def new builtins.map.new)
+  (def __call__ new)
+    
+  (fn keys [m]
+    (vec.map #(vec.first %1) (vec.from m)))
+    
+  (fn values [m]
+    (vec.map #(vec.last %1) (vec.from m)))
+
+  (fn len [m]
+    (vec.len (vec.from m)))
+
+  (fn empty? [m]
+    (eq? (len m) 0))
+
+  (fn is-empty? [m]
+    (empty? m))
+
+  (fn get [m key]
+    (vec.fold
+      (lambda [result pair _]
+        (if (eq? (vec.get pair 0) key)
+            (vec.get pair 1)
+            result))
+      null
+      (vec.from m)))
+
+  (fn put [m key value]
+    (apply apply new (vec.from m) [[key value]]))
+
+  (fn assoc [m key value]
+    (put m key value))
+
+  (fn dissoc [m key]
+    (apply apply new (vec.filter 
+      (lambda [pair _] (nq?
+        (vec.get pair 0)
+        key
+      ))
+      (vec.from m))
+    ))
+
+  (fn has-key? [m key]
+    (if (null? (get m key))
+      false
+      true))
+
+  (fn has-value? [m value]
+    (vec.fold
+      (lambda [result pair _]
+        (seq
+          (def k (vec.get pair 0))
+          (def v (vec.get pair 1))
+          (bool.or result (eq? v value))))
+      false
+      (vec.from m)))
+
+  (fn map [callback m]
+    (apply new (vec.apply-flat (vec.map
+      (lambda [pair _]
+        (seq
+          (def k (vec.get pair 0))
+          (def v (vec.get pair 1))
+          (def new-v (callback v k))
+          [k new-v]))
+      (vec.from m)))))
+
+  (fn filter [callback m]
+    (apply new (vec.apply-flat (vec.filter
+      (lambda [pair _]
+        (seq
+          (def k (vec.get pair 0))
+          (def v (vec.get pair 1))
+          (callback v k)))
+      (vec.from m)))))
+
+  (fn merge [m1 m2]
+    (apply apply new (vec.from m1) (vec.from m2)))
+
+  (fn merge-all []
+    (vec.fold
+      (lambda [acc m _]
+        (merge acc m))
+      (new)
+      %%))
+
+  (fn conj [m other]
+    (if (map.is? other)
+      (merge m other)
+      m))
+)
\ No newline at end of file
diff --git a/modules/core/types/null.owa b/modules/core/types/null.owa
new file mode 100644
index 0000000..2db4848
--- /dev/null
+++ b/modules/core/types/null.owa
@@ -0,0 +1,5 @@
+(seq
+  (def null :null)
+  (fn null? [x]
+    (bool.or (eq? x null) (eq? x :nil)))
+)
\ No newline at end of file
diff --git a/modules/core/types/option.owa b/modules/core/types/option.owa
new file mode 100644
index 0000000..422521d
--- /dev/null
+++ b/modules/core/types/option.owa
@@ -0,0 +1,26 @@
+(seq
+  (namespace option
+    (fn ok <Option>[value]
+      (vec :ok value))
+
+    (fn ok? <Bool>[x]
+      (bool.and
+        (vec? x)
+        (eq? (vec.first x) :ok)))
+
+    (fn err <Option>[value]
+      (vec :err value))
+
+    (fn err? <Bool>[x]
+      (bool.and
+        (vec? x)
+        (eq? (vec.first x) :err)))
+  )
+
+  (fn option? [x]
+    (bool.and
+      (vec? x)
+      (bool.or
+        (eq? (vec.first x) :err)
+        (eq? (vec.first x) :ok))))
+)
\ No newline at end of file
diff --git a/modules/core/types/set.owa b/modules/core/types/set.owa
new file mode 100644
index 0000000..1468da6
--- /dev/null
+++ b/modules/core/types/set.owa
@@ -0,0 +1,60 @@
+(seq
+  (namespace set
+    (def type :set)
+    (def is? (guard type))
+    (fn new [] (apply from %%))
+    (def __call__ new)
+
+    (def fold builtins.set.fold)
+    (def from builtins.set.from)
+
+    (def empty #{})
+    (fn empty? <Bool>[s]
+      (eq? s empty))
+
+    (fn len <Int>[<Set>s]
+      (fold (lambda [acc _] (+ acc 1)) 0 s))
+
+    (fn has <Bool>[<Set>s item]
+      (fold
+        (lambda [acc elem]
+          (bool.or acc (eq? elem item)))
+        false
+        s))
+
+    (fn add <Set>[<Set>s item]
+      (from s [item]))
+
+    (fn remove <Set>[<Set>s item]
+      (fold
+        (lambda [acc elem]
+          (if (eq? elem item)
+            acc
+            (from acc elem)))
+        #{}
+        s))
+
+    (fn union <Set>[]
+      (apply from %%))
+
+    (fn intersection <Set>[<Set>s1 <Set>s2]
+      (fold
+        (lambda [acc elem]
+          (if (has s2 elem)
+            (add acc elem)
+            acc))
+        #{}
+        s1))
+
+    (fn difference <Set>[<Set>s1 <Set>s2]
+      (fold
+        (lambda [acc elem]
+          (if (has s2 elem)
+            acc
+            (add acc elem)))
+        #{}
+        s1))
+  )
+
+  (def set? (guard set.type))
+)
\ No newline at end of file
diff --git a/modules/core/types/str.owa b/modules/core/types/str.owa
new file mode 100644
index 0000000..86b975b
--- /dev/null
+++ b/modules/core/types/str.owa
@@ -0,0 +1,76 @@
+(seq
+  (namespace str
+    (def type :str)
+    (def new builtins.str.new)
+    (def __call__ new)
+    
+    (fn len <Int>[<Str>s]
+      (vec.len (vec.from s)))
+
+    (fn concat <Str>[]
+      (apply new %%))
+
+    (fn empty? <Bool>[<Str>s]
+      (eq? s ""))
+
+    (fn is-empty? <Bool>[<Str>s]
+      (empty? s))
+
+    (fn chars-at <Str>[<Str>s <Int>idx]
+      (vec.get (vec.from s) idx))
+
+    (fn first <Str>[<Str>s]
+      (chars-at s 0))
+
+    (fn last <Str>[<Str>s]
+      (chars-at s (-- (len s))))
+
+    (fn substring <Str>[<Str>s <Int>start <Int>end]
+      (apply concat (vec.slice (vec.from s) start end)))
+
+    (fn substr <Str>[<Str>s <Int>start <Int>len-sub]
+      (substring s start (+ start len-sub)))
+
+    (fn take <Str>[<Str>s <Int>n]
+      (apply concat (vec.take (vec.from s) n)))
+
+    (fn drop <Str>[<Str>s <Int>n]
+      (apply concat (vec.drop (vec.from s) n)))
+
+    (fn reverse <Str>[<Str>s]
+      (apply concat (vec.reverse (vec.from s))))
+
+    (fn starts-with? <Bool>[<Str>s <Str>prefix]
+      (eq? (substring s 0 (len prefix)) prefix))
+
+    (fn ends-with? <Bool>[<Str>s <Str>suffix]
+      (eq? (substring s (- (len s) (len suffix)) (len s)) suffix))
+
+    (fn split <Vec>[<Str>s <Str>sep] (seq
+      (vec.fold
+        (lambda [acc elem _]
+          (if-eq (elem sep)
+            (vec.conj acc "")
+            (vec.conj (vec.take acc (- (len acc) 1)) 
+              (str.concat (vec.last acc) elem)
+            )
+          ))
+        [""]
+        (vec.from s)
+      )))
+
+    (fn join <Str>[<Str>sep <Vec>strs]
+      (if (vec.empty? strs)
+        ""
+        (vec.fold
+          (lambda [acc elem _]
+            (new acc sep elem))
+          (vec.first strs)
+          (vec.tail strs))))
+
+    (fn map <Str>[callback self]
+      (join "" (vec.map callback (vec.from self))))
+  )
+
+  (def str? (guard str.type))
+)
\ No newline at end of file
diff --git a/modules/core/types/struct.owa b/modules/core/types/struct.owa
new file mode 100644
index 0000000..cc3f241
--- /dev/null
+++ b/modules/core/types/struct.owa
@@ -0,0 +1,22 @@
+(seq
+  (defmacro struct [name fields] (seq
+    (for field $fields
+      (if (bool.not (kw? %1))
+        (throw! "Struct fields must be keywords"))
+    )
+    (def $name {
+      :__struct_type__ true
+      :new (lambda [data] (vec.map
+          #(if (map.has-key? data %1)
+            map.get data %1
+            (throw! "Missing field: " %1)
+          )
+          $fields))
+    })
+  ))
+ 
+  (fn struct-type? [v]
+    (if (bool.and (map? v) (map.get v :__struct_type__))
+      true
+      false))
+)
\ No newline at end of file
diff --git a/modules/core/types/vec.owa b/modules/core/types/vec.owa
new file mode 100644
index 0000000..8c7692a
--- /dev/null
+++ b/modules/core/types/vec.owa
@@ -0,0 +1,301 @@
+(namespace vec
+  (def type :vec)
+  (def is? (guard type))
+  (def new builtins.vec.new)
+  (def __call__ new)
+
+  (def fold builtins.vec.fold)
+  (def from builtins.vec.from)
+
+  ;; Empty vector
+  (def empty [])
+
+  ;; Guard to check if a value is a empty vector
+  (fn empty? [<Vec>v]
+    (eq? v empty))
+
+  ;; Get the count of items in a vector
+  (fn len [<Vec>v]
+    (fold (lambda [acc _] (+ acc 1)) 0 v))
+
+  ;; Append an item to the end of a vector
+  (fn conj [<Vec>v item]
+    (apply new v [item]))
+
+  ;; Check if a vector contains an item
+  (fn has [<Vec>v item]
+    (fold
+      (lambda [acc elem _]
+        (bool.or acc (eq? elem item)))
+      false
+      v))
+
+  ;; Get an item from a vector by index
+  (fn get [<Vec>v idx]
+    (fold
+      (lambda [result elem index]
+        (if (eq? index idx)
+          elem
+          result))
+      null
+      v))
+
+  ;; Update an item in a vector
+  ;; If the index is out of bounds, the original vector is returned
+  (fn assoc [<Vec>v <Int>index item]
+    (fold
+      (lambda [acc elem idx]
+        (if (eq? idx index)
+          (conj acc item)
+          (conj acc elem)))
+      []
+      v))
+
+  ;; Remove an item from a vector by index
+  ;; If the index is out of bounds, the original vector is returned
+  (fn remove [<Vec>v <Int>index]
+    (filter
+      (lambda [elem idx]
+        (nq? idx index))
+      v))
+
+  ;; Reverse a vector
+  (fn reverse [<Vec>v]
+    (fold
+      (lambda [acc elem _]
+        (apply merge elem acc))
+      []
+      v))
+
+  ;; Flatten a vector of vectors into a single vector
+  (fn flat [<Vec>v]
+    (fold
+      (lambda [acc elem _]
+        (apply conj [acc elem]))
+      []
+      v))
+
+  ;; Get the first item in a vector
+  (fn first [<Vec>v]
+    (get v 0))
+
+  ;; Get the last item in a vector
+  (fn last [<Vec>v]
+    (get v (-- (len v))))
+
+  ;; Get all items except the first
+  (fn tail [<Vec>v]
+    (filter
+      (lambda [elem idx]
+        (nq? idx 0))
+      v))
+
+  ;; Get the first n items from a vector
+  (fn take [<Vec>v <Int>n]
+    (filter
+      (lambda [elem idx]
+        (lt? idx n))
+      v))
+
+  ;; Get all items except the first n
+  (fn drop [<Vec>v n]
+    (filter
+      (lambda [elem idx]
+        (gte? idx n))
+      v))
+
+  ;; Get all items except the last
+  (fn drop-last [<Vec>v]
+    (filter
+      (lambda [elem idx]
+        (nq? idx (-- (len v))))
+      v))
+
+  (fn enumerate [<Vec>v]
+    (map
+      (lambda [elem idx]
+        (new [idx elem]))
+      v))
+
+  (fn zip [v1 v2]
+    (map
+      (lambda [elem idx]
+        (new elem (get v2 idx)))
+      v1))
+
+  (fn slice [<Vec>v start end]
+    (filter
+      (lambda [elem idx]
+        (bool.and (gte? idx start) (lt? idx end)))
+      v))
+
+  (fn includes? [<Vec>v item]
+    (has v item))
+
+  (fn index-of [<Vec>v item]
+    (fold
+      (lambda [result elem idx]
+        (if (null? result)
+          (if (eq? elem item)
+            idx
+            result)
+          result))
+      null
+      v))
+
+  (fn join-str [sep v]
+    (if (empty? v)
+      ""
+      (fold
+        (lambda [acc elem _]
+          (str.new acc sep elem))
+        (first v)
+        (tail v))))
+
+  ;; Map a callback to each item in a vector
+  (fn map [callback <Vec>v]
+    (fold
+      (lambda [acc elem index]
+        (apply conj [acc (callback elem index)]))
+      []
+      v))
+
+  ;; Filter a vector by a callback
+  (fn filter [callback <Vec>v]
+    (fold
+      (lambda [acc elem index]
+        (if (callback elem index)
+          (apply conj [acc elem])
+          acc))
+      []
+      v))
+
+  ;; Find the first item that matches the callback
+  (fn find [callback <Vec>v]
+    (fold
+      (lambda [result elem index]
+        (if (null? result)
+          (if (callback elem index)
+            elem
+            result)
+          result))
+      null
+      v))
+
+  ;; Check if every item in a vector matches the callback
+  ;; TODO: Break at first non-match for better performance
+  (fn every? <Bool>[callback <Vec>v]
+    (fold
+      (lambda [result elem idx]
+        (bool.and result (callback elem idx)))
+      true
+      v))
+
+  ;; Check if any item in a vector matches the callback
+  ;; TODO: Break at first match for better performance
+  (fn some? <Bool>[callback <Vec>v]
+    (fold
+      (lambda [result elem idx]
+        (bool.or result (callback elem idx)))
+      false
+      v))
+
+  ;; Reduce a vector into a single value
+  (fn reduce <Bool>[callback initial <Vec>v]
+    (fold callback initial v))
+
+  ;; Count the number of items that match the callback
+  (fn count [callback v]
+    (fold
+      (lambda [count elem idx]
+        (if (callback elem idx)
+          (+ count 1)
+          count))
+      0
+      v))
+
+  ;; Merge all vectors into a single vector
+  (fn merge []
+    (fold
+      (lambda [acc elem _]
+        (apply conj [acc elem]))
+      []
+      %%))
+
+  (fn max-by [comparator v]
+    (fold
+      (lambda [current elem _]
+        (if (null? current)
+          elem
+          (if (eq? (comparator elem current) :greater)
+            elem
+            current)))
+      null
+      v))
+
+  (fn min-by [comparator v]
+    (fold
+      (lambda [current elem _]
+        (if (null? current)
+          elem
+          (if (eq? (comparator elem current) :less)
+            elem
+            current)))
+      null
+      v))
+
+  (fn uniq [<Vec>v]
+    (fold
+      (lambda [result elem _]
+        (if (has result elem)
+          result
+          (conj result elem)))
+      []
+      v))
+
+  (fn partition [callback v]
+    (fold
+      (lambda [result elem idx]
+        (seq
+          (def group (if (callback elem idx) 0 1))
+          (def current-part (get result group))
+          (assoc result group (conj current-part elem))))
+      [[] []]
+      v))
+
+  (fn group-by [key-fn v]
+    (fold
+      (lambda [result elem idx]
+        (seq
+          (def key (key-fn elem idx))
+          (def group (map.get result key))
+          (def new-group (if (null? group) [] group))
+          (map.put result key (conj new-group elem))))
+      (map.new)
+      v))
+
+  (fn flatten [<Vec>v]
+    (fold
+      (lambda [result elem _]
+        (if (vec.is? elem)
+          (conj result (flatten elem))
+          (conj result elem)))
+      []
+      v))
+
+  (fn distinct [<Vec>v]
+    (uniq v))
+
+  (fn compact [<Vec>v]
+    (filter
+      (lambda [elem _]
+        (not (null? elem)))
+      v))
+
+  (fn sum [<Vec>v]
+    (fold
+      (lambda [acc elem _]
+        (+ acc elem))
+      0
+      v))
+)
\ No newline at end of file
diff --git a/modules/owu/cli/main.owa b/modules/owu/cli/main.owa
new file mode 100644
index 0000000..ec6db3a
--- /dev/null
+++ b/modules/owu/cli/main.owa
@@ -0,0 +1,19 @@
+(seq
+  (def cmd (vec.first argv))
+  (def args (vec.tail argv))
+
+  (if (bool.or (null? cmd) (str.starts-with? cmd "-")) (seq
+    (trace "Error: No command specified")
+    (return 1)
+  ))
+
+  (try
+    (match cmd
+      ("run" (include "run"))
+      (_ (trace "Error: Command '" cmd "' not found"))
+    )
+    (lambda [msg type] (seq
+      (trace type ": " msg)
+      (return 1)))
+  )
+)
\ No newline at end of file
diff --git a/modules/owu/cli/run.owa b/modules/owu/cli/run.owa
new file mode 100644
index 0000000..3485351
--- /dev/null
+++ b/modules/owu/cli/run.owa
@@ -0,0 +1,43 @@
+(seq
+  (def target (vec.find #(bool.not (str.starts-with? %1 "-")) (vec.reverse args)))
+  (if (null? target) (seq
+    (trace "No target specified")
+    (return)
+  ))
+
+  (fn parse-arg [args name] (seq
+    (def idx (vec.index-of args name))
+    (if (null? idx)
+      null
+      (vec.get args (+ idx 1))
+    )
+  ))
+
+  (def no-builtins? (vec.has args "--no-builtins"))
+  (def no-core? (vec.has args "--no-core"))
+  (def no-std? (vec.has args "--no-std"))
+  (def is-debug? (vec.has args "--debug"))
+  (def test-target (parse-arg args "--test"))
+
+  (exec
+    {
+      :__runtime__ :owu
+      :__dir__ ""
+      :__main__ target
+      :__test__ test-target
+    }
+    (seq
+      (unless no-builtins?
+        (def builtins builtins))
+
+      (unless (bool.or no-builtins? no-core?)
+        (include (str.concat modules-dir "/core")))
+
+      (unless (bool.or no-builtins? no-core? no-std?)
+        (include (str.concat modules-dir "/std")))
+
+      (def __is_debug__ is-debug?)
+    )
+    target
+  )
+)
diff --git a/modules/owu/main.owa b/modules/owu/main.owa
new file mode 100644
index 0000000..08651e7
--- /dev/null
+++ b/modules/owu/main.owa
@@ -0,0 +1,15 @@
+(builtins.seq
+  (builtins.include "../core")
+  (builtins.include "../std")
+  (namespace owu
+    (def argv (platform.args))
+    (def modules-dir (str.concat __dir__ "/.."))
+
+    (if (eq? (vec.len argv) 0) (seq
+      (return 1)
+    ))
+
+    (include "cli")
+    (return 0)
+  )
+)
\ No newline at end of file
diff --git a/modules/std/main.owa b/modules/std/main.owa
new file mode 100644
index 0000000..4fb9ad2
--- /dev/null
+++ b/modules/std/main.owa
@@ -0,0 +1,6 @@
+(seq
+  (include "platform")
+  (include "path")
+
+  (test.space "std" (include "tests/main"))
+)
\ No newline at end of file
diff --git a/modules/std/path.owa b/modules/std/path.owa
new file mode 100644
index 0000000..dd555d5
--- /dev/null
+++ b/modules/std/path.owa
@@ -0,0 +1,222 @@
+(namespace path
+  ;; Platform-specific path separator.
+  (def sep (match platform.os-family
+    (:windows "\\")
+    (_ "/")
+  ))
+
+  ;; Internal: converts "/" to "\" on Windows; no-op on other platforms.
+  (fn norm-seps <Str>[<Str>p]
+    (match platform.os-family
+      (:windows (str.map (lambda [c _] (if (eq? c "/") "\\" c)) p))
+      (_ p)))
+
+  ;; Returns the root prefix of a path.
+  ;;
+  ;;   Unix    — "/"    for paths starting with "/", "" for relative.
+  ;;   Windows — "\"   for UNC/rooted paths ("\" or "/" prefix)
+  ;;             "X:\" for drive-letter absolute paths ("X:\" or "X:/")
+  ;;             ""    for all relative paths ("X:path" is relative on Windows)
+  (fn root <Str>[<Str>p]
+    (match platform.os-family
+      (:windows
+        (if (bool.or (str.starts-with? p "\\") (str.starts-with? p "/"))
+          "\\"
+          (if (bool.and (gte? (str.len p) 3)
+                        (bool.and (eq? (str.chars-at p 1) ":")
+                                  (bool.or (eq? (str.chars-at p 2) "\\")
+                                           (eq? (str.chars-at p 2) "/"))))
+            (str.concat (str.take p 2) "\\")
+            "")))
+      (_ (if (str.starts-with? p "/") "/" ""))
+    ))
+
+  ;; Returns true if the path is absolute (has a non-empty root prefix).
+  (fn absolute? <Bool>[<Str>p]
+    (bool.not (str.empty? (root p))))
+
+  ;; Returns true if the path is relative (has no root prefix).
+  (fn relative? <Bool>[<Str>p]
+    (bool.not (absolute? p)))
+
+  ;; Splits a path into its string components using the platform separator.
+  ;; On Windows "/" is also accepted as a separator.
+  ;; The root prefix (if any) is preserved as the first component so that
+  ;; split + join is a round-trip operation.
+  (fn split <Vec>[<Str>p]
+    (if (str.empty? p)
+      []
+      (str.split (norm-seps p) sep)))
+
+  ;; Joins path components with the platform separator.
+  (fn join <Str>[<Vec>p]
+    (str.join sep p))
+
+  ;; Removes "." components, resolves ".." components, and returns the
+  ;; canonical form of the path using the platform separator.
+  ;;
+  ;; Bug fixes vs. previous version:
+  ;;   • absolute paths that collapse entirely return the root (e.g. "/" not "")
+  ;;   • Windows drive-letter paths no longer get a spurious leading "\"
+  (fn normalize <Str>[<Str>p]
+    (seq
+      (def r (root p))
+      ;; Work only on the non-root body so that root components never
+      ;; participate in ".." resolution.
+      (def body (norm-seps (str.drop p (str.len r))))
+      (def parts (if (str.empty? body) [] (str.split body sep)))
+      (def normalized [])
+      (for part parts
+        (if (bool.or (eq? part ".") (str.empty? part)) (continue))
+        (set! normalized (if (eq? part "..")
+          (vec.drop-last normalized)
+          (vec.conj normalized part))))
+      (def result (join normalized))
+      (if (str.empty? r)
+        result
+        (if (str.empty? result)
+          r
+          (str.concat r result)))))
+
+  ;; Returns the parent directory of the path.
+  ;;   • Paths directly under the root return the root string.
+  ;;   • Top-level relative paths (e.g. "a") return "".
+  ;;
+  ;; Bug fix vs. previous version: returns sep-based root, not hardcoded "/".
+  (fn parent <Str>[<Str>p] (seq
+    (def norm (normalize p))
+    (def r (root norm))
+    (def body (str.drop norm (str.len r)))
+    (def parts (if (str.empty? body)
+      []
+      (vec.filter
+        (lambda [part _] (bool.not (str.empty? part)))
+        (str.split body sep))))
+    (def parent-parts (vec.drop-last parts))
+    (if (vec.empty? parent-parts)
+      r
+      (str.concat r (join parent-parts)))))
+
+  ;; Returns the last component of the path (filename or final directory name).
+  ;; Returns "" for paths that end with a separator.
+  (fn basename <Str>[<Str>p] (seq
+    (def parts (split p))
+    (if (vec.empty? parts) "" (vec.last parts))))
+
+  ;; Returns the file extension including the leading dot, or "" if none.
+  ;;
+  ;; Rules:
+  ;;   • Hidden files whose name starts with "." have no extension.
+  ;;   • A trailing dot (e.g. "file.") is not considered an extension.
+  ;;   • Only the last dot in the basename is used (e.g. "a.tar.gz" → ".gz").
+  ;;
+  ;; Examples:
+  ;;   "file.txt"     → ".txt"
+  ;;   "archive.tar.gz" → ".gz"
+  ;;   "file"         → ""
+  ;;   ".hidden"      → ""
+  ;;   "file."        → ""
+  (fn ext <Str>[<Str>p] (seq
+    (def base (basename p))
+    (def dot-idx (vec.fold
+      (lambda [acc elem idx]
+        (if (eq? elem ".") idx acc))
+      -1
+      (vec.from base)))
+    (if (bool.or (lte? dot-idx 0) (eq? dot-idx (-- (str.len base))))
+      ""
+      (str.drop base dot-idx))))
+
+  ;; Returns the filename without its extension.
+  ;;
+  ;; Examples:
+  ;;   "file.txt"     → "file"
+  ;;   "archive.tar.gz" → "archive.tar"
+  ;;   "file"         → "file"
+  ;;   ".hidden"      → ".hidden"
+  (fn stem <Str>[<Str>p] (seq
+    (def base (basename p))
+    (def e (ext p))
+    (if (str.empty? e)
+      base
+      (str.take base (- (str.len base) (str.len e))))))
+
+  ;; Returns the path with its extension replaced by new-ext.
+  ;; Pass "" as new-ext to strip the extension entirely.
+  ;; The directory prefix and stem are preserved unchanged.
+  ;;
+  ;; Examples:
+  ;;   (with-ext "file.txt" ".md")  → "file.md"
+  ;;   (with-ext "file.txt" "")     → "file"
+  ;;   (with-ext "file"     ".txt") → "file.txt"
+  (fn with-ext <Str>[<Str>p <Str>new-ext] (seq
+    (def e (ext p))
+    (def without-ext
+      (if (str.empty? e)
+        p
+        (str.take p (- (str.len p) (str.len e)))))
+    (str.concat without-ext new-ext)))
+
+  ;; Resolves path relative to base and returns the normalized result.
+  ;; If path is already absolute it is returned normalized, ignoring base.
+  ;; Otherwise base + sep + path is normalized.
+  ;;
+  ;; Examples (Unix):
+  ;;   (resolve "/base"     "file.txt")   → "/base/file.txt"
+  ;;   (resolve "/base/dir" "../file.txt") → "/base/file.txt"
+  ;;   (resolve "/other"    "/abs")       → "/abs"
+  (fn resolve <Str>[<Str>base <Str>p]
+    (if (absolute? p)
+      (normalize p)
+      (normalize (str.concat base sep p))))
+
+  ;; Computes the relative path from base to target.
+  ;;
+  ;;   • Returns "." when base and target are the same path.
+  ;;   • When the roots differ (e.g. different Windows drive letters)
+  ;;     the normalized target is returned unchanged.
+  ;;
+  ;; Examples (Unix):
+  ;;   (relative-to "/a/b"   "/a/b/c/d") → "c/d"
+  ;;   (relative-to "/a/b"   "/a/c")     → "../c"
+  ;;   (relative-to "/a/b/c" "/a")       → "../.."
+  ;;   (relative-to "/a/b"   "/a/b")     → "."
+  (fn relative-to <Str>[<Str>base <Str>target] (seq
+    (def norm-base   (normalize base))
+    (def norm-target (normalize target))
+    (def base-r   (root norm-base))
+    (def target-r (root norm-target))
+    (if (nq? base-r target-r)
+      norm-target
+      (seq
+        (def base-body   (str.drop norm-base   (str.len base-r)))
+        (def target-body (str.drop norm-target (str.len target-r)))
+        (fn parts-of [body]
+          (if (str.empty? body)
+            []
+            (vec.filter
+              (lambda [part _] (bool.not (str.empty? part)))
+              (str.split body sep))))
+        (def base-parts   (parts-of base-body))
+        (def target-parts (parts-of target-body))
+        (def base-len   (vec.len base-parts))
+        (def target-len (vec.len target-parts))
+        ;; Find length of the common prefix.
+        (def i 0)
+        (while (bool.and (lt? i base-len)
+                         (bool.and (lt? i target-len)
+                                   (eq? (vec.get base-parts i)
+                                        (vec.get target-parts i))))
+          (set! i (++ i)))
+        ;; One ".." per remaining component in base, then the remaining target components.
+        (def ups       (vec.map (lambda [_e _i] "..") (vec.drop base-parts i)))
+        (def remaining (vec.drop target-parts i))
+        (def result-parts
+          (vec.fold
+            (lambda [acc elem _] (vec.conj acc elem))
+            ups
+            remaining))
+        (if (vec.empty? result-parts)
+          "."
+          (join result-parts))))))
+)
diff --git a/modules/std/platform.owa b/modules/std/platform.owa
new file mode 100644
index 0000000..8162437
--- /dev/null
+++ b/modules/std/platform.owa
@@ -0,0 +1,55 @@
+(namespace platform
+  (def os-name builtins.platform.os-name)
+  (def os-family builtins.platform.os-family)
+  (def arch builtins.platform.arch)
+  (def argv builtins.platform.argv)
+  (def executable #(vec.get (argv) 0))
+  (def args #(vec.slice (argv) 1 (vec.len (argv))))
+  
+  (def debug? (lookup __is_debug__ false))
+
+  (def os-names [
+    :linux
+    :windows
+    :macos
+    :android
+    :ios
+    :openbsd
+    :freebsd
+    :netbsd
+    :wasi
+    :hermit
+    :aix
+    :apple
+    :dragonfly
+    :emscripten
+    :espidf
+    :fortanix
+    :uefi
+    :fuchsia
+    :haiku
+    :hermit
+    :watchos
+    :visionos
+    :tvos
+    :horizon
+    :hurd
+    :illumos
+    :l4re
+    :nto
+    :redox
+    :solaris
+    :solid_asp3
+    :vexos
+    :vita
+    :vxworks
+    :xous
+  ])
+
+  (def os-families [
+    :unix
+    :windows
+    :itron
+    :wasm
+  ])
+)
\ No newline at end of file
diff --git a/modules/std/tests/main.owa b/modules/std/tests/main.owa
new file mode 100644
index 0000000..2b58fc9
--- /dev/null
+++ b/modules/std/tests/main.owa
@@ -0,0 +1,3 @@
+(seq
+  (include "path")
+)
\ No newline at end of file
diff --git a/modules/std/tests/path.owa b/modules/std/tests/path.owa
new file mode 100644
index 0000000..5825c37
--- /dev/null
+++ b/modules/std/tests/path.owa
@@ -0,0 +1,286 @@
+(namespace test.path
+  (test.case "path.sep"
+    (assert.eq! path.sep (match platform.os-family (:windows "\\") (_ "/")))
+  )
+
+  (test.case "path.root"
+    ;; Relative paths and empty string have no root on all platforms.
+    (assert.eq! (path.root "relative") "")
+    (assert.eq! (path.root "") "")
+    (match platform.os-family
+      (:windows (seq
+        ;; Rooted by backslash or forward-slash → canonical "\"
+        (assert.eq! (path.root "\\a\\b") "\\")
+        (assert.eq! (path.root "/a/b")   "\\")
+        ;; Drive-letter absolute ("X:\" or "X:/")
+        (assert.eq! (path.root "C:\\a\\b") "C:\\")
+        (assert.eq! (path.root "C:/a/b")   "C:\\")
+        (assert.eq! (path.root "C:\\")     "C:\\")
+        ;; Drive letter WITHOUT a separator is relative on Windows
+        (assert.eq! (path.root "C:")         "")
+        (assert.eq! (path.root "C:relative") "")
+      ))
+      (_ (seq
+        (assert.eq! (path.root "/")     "/")
+        (assert.eq! (path.root "/a/b")  "/")
+      ))
+    )
+  )
+
+  (test.case "path.absolute?"
+    ;; "/" is recognised as absolute on all platforms.
+    (assert.ok! (path.absolute? "/absolute/unix"))
+    (assert.ok! (path.absolute? "/"))
+    (assert.not! (path.absolute? "relative/unix"))
+    (assert.not! (path.absolute? "./relative/unix"))
+    (match platform.os-family
+      (:windows (seq
+        ;; Drive-letter prefix (both separators)
+        (assert.ok! (path.absolute? "C:\\absolute\\windows"))
+        (assert.ok! (path.absolute? "C:/absolute/windows"))
+        ;; UNC / rooted backslash
+        (assert.ok! (path.absolute? "\\absolute\\unc"))
+        ;; Relative Windows paths
+        (assert.not! (path.absolute? "relative\\windows"))
+        (assert.not! (path.absolute? ".\\relative\\windows"))
+        ;; Drive letter without separator is relative
+        (assert.not! (path.absolute? "C:relative"))
+      ))
+      (_ (void))
+    )
+  )
+
+  (test.case "path.relative?"
+    (assert.ok! (path.relative? "relative/unix"))
+    (assert.not! (path.relative? "/absolute/unix"))
+    (match platform.os-family
+      (:windows (seq
+        (assert.ok! (path.relative? "relative\\windows"))
+        (assert.not! (path.relative? "C:\\absolute\\windows"))
+        (assert.not! (path.relative? "\\absolute\\unc"))
+        (assert.ok! (path.relative? "C:relative"))
+      ))
+      (_ (void))
+    )
+  )
+
+  (test.case "path.split"
+    (assert.eq! (path.split "") [])
+    (assert.eq! (path.split "a") ["a"])
+    (match platform.os-family
+      (:windows (seq
+        (assert.eq! (path.split "a\\b\\c") ["a" "b" "c"])
+        ;; Windows also accepts "/" as separator
+        (assert.eq! (path.split "a/b/c") ["a" "b" "c"])
+        ;; Drive-letter prefix is kept as the first component (round-trip with join)
+        (assert.eq! (path.split "C:\\a\\b") ["C:" "a" "b"])
+        (assert.eq! (path.split "C:/a/b")   ["C:" "a" "b"])
+      ))
+      (_ (seq
+        (assert.eq! (path.split "a/b/c") ["a" "b" "c"])
+      ))
+    )
+  )
+
+  (test.case "path.join"
+    (assert.eq! (path.join []) "")
+    (assert.eq! (path.join ["a"]) "a")
+    (match platform.os-family
+      (:windows (seq
+        (assert.eq! (path.join ["a" "b" "c"]) "a\\b\\c")
+        (assert.eq! (path.join ["C:" "a" "b"]) "C:\\a\\b")
+      ))
+      (_ (seq
+        (assert.eq! (path.join ["a" "b" "c"]) (str.concat "a" path.sep "b" path.sep "c"))
+      ))
+    )
+  )
+
+  (test.case "path.normalize"
+    (match platform.os-family
+      (:windows (seq
+        ;; Dot component is stripped
+        (assert.eq! (path.normalize "a\\.\\b") (path.join ["a" "b"]))
+        ;; Double-dot collapses parent
+        (assert.eq! (path.normalize "a\\..\\b") "b")
+        ;; Rooted-backslash absolute path
+        (assert.eq! (path.normalize "\\a\\..\\b") (str.concat path.sep "b"))
+        ;; Bug fix: absolute path collapsing to root returns the root, not ""
+        (assert.eq! (path.normalize "\\")       "\\")
+        (assert.eq! (path.normalize "\\a\\..")  "\\")
+        ;; Drive-letter paths: no spurious leading "\" added
+        (assert.eq! (path.normalize "C:\\a\\..\\b")    "C:\\b")
+        (assert.eq! (path.normalize "C:\\")             "C:\\")
+        (assert.eq! (path.normalize "C:\\a\\b\\..\\..")  "C:\\")
+        ;; Windows normalises "/" separators as well
+        (assert.eq! (path.normalize "a/./b")  (path.join ["a" "b"]))
+        (assert.eq! (path.normalize "C:/a/../b") "C:\\b")
+      ))
+      (_ (seq
+        ;; Dot component is stripped
+        (assert.eq! (path.normalize "a/./b") (path.join ["a" "b"]))
+        ;; Double-dot collapses parent
+        (assert.eq! (path.normalize "a/../b") "b")
+        ;; Rooted absolute path
+        (assert.eq! (path.normalize "/a/../b") (str.concat path.sep "b"))
+        ;; Bug fix: absolute path collapsing to root returns "/", not ""
+        (assert.eq! (path.normalize "/")       "/")
+        (assert.eq! (path.normalize "/a/..")   "/")
+        (assert.eq! (path.normalize "/a/b/../..") "/")
+      ))
+    )
+  )
+
+  (test.case "path.parent"
+    ;; Top-level relative path always returns "" on every platform.
+    (assert.eq! (path.parent "a") "")
+    (match platform.os-family
+      (:windows (seq
+        (assert.eq! (path.parent "a\\b\\c") "a\\b")
+        (assert.eq! (path.parent "a\\b")    "a")
+        ;; Bug fix: rooted paths return "\" not hardcoded "/"
+        (assert.eq! (path.parent "\\")                  "\\")
+        (assert.eq! (path.parent "\\..\\a\\.\\..\\")    "\\")
+        ;; Drive-letter paths
+        (assert.eq! (path.parent "C:\\")      "C:\\")
+        (assert.eq! (path.parent "C:\\a")     "C:\\")
+        (assert.eq! (path.parent "C:\\a\\b")  "C:\\a")
+        (assert.eq! (path.parent "C:\\a\\b\\c") "C:\\a\\b")
+      ))
+      (_ (seq
+        (assert.eq! (path.parent "a/b/c") "a/b")
+        (assert.eq! (path.parent "a/b")   "a")
+        (assert.eq! (path.parent "/")     "/")
+        (assert.eq! (path.parent "/../a/./../") "/")
+      ))
+    )
+  )
+
+  (test.case "path.basename"
+    (assert.eq! (path.basename "file.txt") "file.txt")
+    (match platform.os-family
+      (:windows (seq
+        (assert.eq! (path.basename "a\\b\\c") "c")
+        ;; Trailing separator → empty basename
+        (assert.eq! (path.basename "a\\b\\") "")
+        (assert.eq! (path.basename "C:\\Users\\file.txt") "file.txt")
+        ;; Windows also handles "/" separator
+        (assert.eq! (path.basename "a/b/c") "c")
+      ))
+      (_ (seq
+        (assert.eq! (path.basename "a/b/c") "c")
+        (assert.eq! (path.basename "a/b/")  "")
+      ))
+    )
+  )
+
+  (test.case "path.ext"
+    ;; Basic cases work on all platforms (basename is a simple name)
+    (assert.eq! (path.ext "file.txt")       ".txt")
+    (assert.eq! (path.ext "file")           "")
+    (assert.eq! (path.ext ".hidden")        "")
+    (assert.eq! (path.ext "archive.tar.gz") ".gz")
+    (assert.eq! (path.ext "file.")          "")
+    (assert.eq! (path.ext "")              "")
+    (match platform.os-family
+      (:windows (seq
+        (assert.eq! (path.ext "C:\\Users\\file.txt") ".txt")
+        (assert.eq! (path.ext "a\\b\\no-ext")        "")
+      ))
+      (_ (seq
+        (assert.eq! (path.ext "a/b/file.txt") ".txt")
+        (assert.eq! (path.ext "a/b/no-ext")   "")
+      ))
+    )
+  )
+
+  (test.case "path.stem"
+    (assert.eq! (path.stem "file.txt")       "file")
+    (assert.eq! (path.stem "file")           "file")
+    (assert.eq! (path.stem ".hidden")        ".hidden")
+    (assert.eq! (path.stem "archive.tar.gz") "archive.tar")
+    (assert.eq! (path.stem "")              "")
+    (match platform.os-family
+      (:windows (seq
+        (assert.eq! (path.stem "C:\\Users\\file.txt") "file")
+      ))
+      (_ (seq
+        (assert.eq! (path.stem "a/b/file.txt") "file")
+      ))
+    )
+  )
+
+  (test.case "path.with-ext"
+    (assert.eq! (path.with-ext "file.txt" ".md")  "file.md")
+    (assert.eq! (path.with-ext "file.txt" "")     "file")
+    (assert.eq! (path.with-ext "file"     ".txt") "file.txt")
+    (assert.eq! (path.with-ext "archive.tar.gz" ".bz2") "archive.tar.bz2")
+    ;; Hidden file: no extension → new-ext is appended
+    (assert.eq! (path.with-ext ".hidden" ".txt") ".hidden.txt")
+    ;; Directory prefix is preserved
+    (match platform.os-family
+      (:windows (seq
+        (assert.eq! (path.with-ext "C:\\a\\file.txt" ".md") "C:\\a\\file.md")
+      ))
+      (_ (seq
+        (assert.eq! (path.with-ext "a/b/file.txt" ".md") "a/b/file.md")
+      ))
+    )
+  )
+
+  (test.case "path.resolve"
+    (match platform.os-family
+      (:windows (seq
+        ;; Relative path is joined to base and normalized
+        (assert.eq! (path.resolve "C:\\base"     "file.txt")     "C:\\base\\file.txt")
+        ;; ".." is resolved against base
+        (assert.eq! (path.resolve "C:\\base\\dir" "..\\file.txt") "C:\\base\\file.txt")
+        ;; Absolute path ignores base
+        (assert.eq! (path.resolve "C:\\other"    "C:\\absolute") "C:\\absolute")
+        ;; Deep traversal
+        (assert.eq! (path.resolve "C:\\a\\b\\c"  "..\\..\\d")    "C:\\a\\d")
+      ))
+      (_ (seq
+        (assert.eq! (path.resolve "/base"     "file.txt")    "/base/file.txt")
+        (assert.eq! (path.resolve "/base/dir" "../file.txt") "/base/file.txt")
+        ;; Absolute path ignores base
+        (assert.eq! (path.resolve "/other"    "/absolute")   "/absolute")
+        ;; Deep traversal
+        (assert.eq! (path.resolve "/a/b/c"    "../../d")     "/a/d")
+        ;; Relative base + relative path
+        (assert.eq! (path.resolve "base/dir"  "file.txt")    "base/dir/file.txt")
+      ))
+    )
+  )
+
+  (test.case "path.relative-to"
+    (match platform.os-family
+      (:windows (seq
+        ;; Child path
+        (assert.eq! (path.relative-to "C:\\a\\b"   "C:\\a\\b\\c\\d") "c\\d")
+        ;; Sibling path
+        (assert.eq! (path.relative-to "C:\\a\\b"   "C:\\a\\c")       "..\\c")
+        ;; Ancestor path
+        (assert.eq! (path.relative-to "C:\\a\\b\\c" "C:\\a")         "..\\..")
+        ;; Same path → "."
+        (assert.eq! (path.relative-to "C:\\a\\b"   "C:\\a\\b")       ".")
+        ;; From root
+        (assert.eq! (path.relative-to "C:\\"       "C:\\a\\b")       "a\\b")
+        ;; Different drives → return normalized target unchanged
+        (assert.eq! (path.relative-to "C:\\a"      "D:\\b")          "D:\\b")
+      ))
+      (_ (seq
+        (assert.eq! (path.relative-to "/a/b"   "/a/b/c/d") "c/d")
+        (assert.eq! (path.relative-to "/a/b"   "/a/c")     "../c")
+        (assert.eq! (path.relative-to "/a/b/c" "/a")       "../..")
+        ;; Same path → "."
+        (assert.eq! (path.relative-to "/a/b"   "/a/b")     ".")
+        ;; From root
+        (assert.eq! (path.relative-to "/"      "/a/b")     "a/b")
+        ;; Relative paths
+        (assert.eq! (path.relative-to "a/b"    "a/b/c")    "c")
+        (assert.eq! (path.relative-to "a/b"    "a/c")      "../c")
+      ))
+    )
+  )
+)
diff --git a/src/builtins/ast.rs b/src/builtins/ast.rs
new file mode 100644
index 0000000..e1afbe8
--- /dev/null
+++ b/src/builtins/ast.rs
@@ -0,0 +1,14 @@
+use crate::core::{OwaValue, Scope, except_arity};
+
+#[must_use]
+pub fn owa_pack() -> OwaValue {
+    OwaValue::native_macro(|_, _, args| {
+        let [arg] = except_arity(args)?;
+        Ok(arg.pack().into())
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([("pack", owa_pack())])
+}
diff --git a/src/builtins/cond.rs b/src/builtins/cond.rs
new file mode 100644
index 0000000..7edf98e
--- /dev/null
+++ b/src/builtins/cond.rs
@@ -0,0 +1,97 @@
+use crate::{
+    core::{OwaError, OwaValue, Scope, except_arity, except_arity_min},
+    parser::ast::OwaAst,
+};
+
+#[must_use]
+pub fn owa_if_eq() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [cond_ast, then_ast, else_ast] = except_arity(args)?;
+        let cond_ast = cond_ast.as_call()?;
+
+        let mut result = true;
+        let mut prev = None;
+        for arg in cond_ast {
+            if !result {
+                break;
+            }
+            // Condition args are evaluated as values (control-flow here is a programming error)
+            let arg = interpreter.eval_value(arg, scope_id)?;
+            if let Some(prev) = prev {
+                result = prev == arg;
+            }
+            prev = Some(arg);
+        }
+
+        if result {
+            // Branch body — propagate Completion (break/continue/return pass through)
+            interpreter.eval(then_ast, scope_id)
+        } else {
+            interpreter.eval(else_ast, scope_id)
+        }
+    })
+}
+
+#[must_use]
+pub fn owa_if_has() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [target_ast, cond_ast, then_ast, else_ast] = except_arity(args)?;
+        let target_ast = interpreter.eval_value(target_ast, scope_id)?;
+        let items_ast = cond_ast.as_call()?;
+
+        for arg in items_ast {
+            let arg = interpreter.eval_value(arg, scope_id)?;
+            if arg == target_ast {
+                return interpreter.eval(then_ast, scope_id);
+            }
+        }
+
+        interpreter.eval(else_ast, scope_id)
+    })
+}
+
+#[must_use]
+pub fn owa_match() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let ([value_ast], branches) = except_arity_min(args)?;
+        // Evaluate the matched value
+        let value = interpreter.eval_value(value_ast, scope_id)?;
+        let mut default = None;
+
+        for branch in branches {
+            let branch = branch.as_call()?;
+
+            let [pattern_ast, expr_ast] = except_arity(branch)?;
+            if pattern_ast == &OwaAst::sym("_") {
+                default = Some(expr_ast);
+                continue;
+            }
+
+            // Evaluate pattern as a value
+            let pattern = interpreter.eval_value(pattern_ast, scope_id)?;
+
+            if pattern == value {
+                // Branch body — propagate Completion
+                return interpreter.eval(expr_ast, scope_id);
+            }
+        }
+
+        default.map_or_else(
+            || {
+                Err(OwaError::RuntimeError(OwaValue::Str(
+                    "Unmatched pattern".into(),
+                )))
+            },
+            |default| interpreter.eval(default, scope_id),
+        )
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("if_eq", owa_if_eq()),
+        ("if_has", owa_if_has()),
+        ("match", owa_match()),
+    ])
+}
diff --git a/src/builtins/errors.rs b/src/builtins/errors.rs
new file mode 100644
index 0000000..dd3ac02
--- /dev/null
+++ b/src/builtins/errors.rs
@@ -0,0 +1,83 @@
+use crate::{
+    core::{Completion, OwaError, OwaValue, Scope, except_arity, except_arity_min},
+    parser::ast::OwaAst,
+};
+
+#[must_use]
+pub fn owa_throw_panic() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [message] = except_arity(args)?;
+        let message = message.as_str()?;
+        Err(OwaError::Panic(message.to_string()))
+    })
+}
+
+#[must_use]
+pub fn owa_throw_type_error() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [expected, got] = except_arity(args)?;
+        let expected = expected.as_str()?;
+        let got = got.as_str()?;
+        Err(OwaError::TypeError(expected.to_string(), got.to_string()))
+    })
+}
+
+#[must_use]
+pub fn owa_throw_arity_error() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [expected, got] = except_arity(args)?;
+        let expected = expected.as_int()?;
+        let got = got.as_int()?;
+        Err(OwaError::ArityError(expected as usize, got as usize))
+    })
+}
+
+#[must_use]
+pub fn owa_throw_runtime_error() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [value] = except_arity(args)?;
+        Err(OwaError::RuntimeError(value.clone()))
+    })
+}
+
+#[must_use]
+pub fn owa_try_catch() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let ([try_expr], catch_exprs) = except_arity_min(args)?;
+
+        // Normalise both signal channels first so that control-flow signals
+        // (e.g. `break` inside try) are never mistaken for real errors.
+        match Completion::from_result(interpreter.eval(try_expr, scope_id)) {
+            // Propagate any completion (Value, Break, Continue, Return) unchanged
+            Ok(completion) => Ok(completion),
+            // Signal errors that escaped normalisation are also propagated
+            Err(OwaError::Signal(f)) => Ok(f.into()),
+            Err(err) => {
+                for catch_expr in catch_exprs {
+                    let catch_call = OwaAst::call([
+                        catch_expr.clone(),
+                        OwaAst::str(err.message()),
+                        OwaAst::kw(err.type_name()),
+                    ]);
+                    // Run catch handler; propagate control flow if it emits any
+                    match Completion::from_result(interpreter.eval(&catch_call, scope_id))? {
+                        Completion::Value(_) => {} // discard value
+                        c => return Ok(c),         // propagate Break/Continue/Return
+                    }
+                }
+                Err(OwaError::Panic(format!("Unhandled error: {err}")))
+            }
+        }
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("throw_panic", owa_throw_panic()),
+        ("throw_type_error", owa_throw_type_error()),
+        ("throw_arity_error", owa_throw_arity_error()),
+        ("throw_runtime_error", owa_throw_runtime_error()),
+        ("try", owa_try_catch()),
+    ])
+}
diff --git a/src/builtins/ffi.rs b/src/builtins/ffi.rs
new file mode 100644
index 0000000..489ab9b
--- /dev/null
+++ b/src/builtins/ffi.rs
@@ -0,0 +1,299 @@
+use std::{
+    collections::HashMap,
+    ffi::{CStr, CString, c_char, c_void},
+    sync::{Mutex, OnceLock},
+};
+
+use libffi::middle::{Arg, Cif, CodePtr, Type};
+use libloading::Library;
+
+use crate::core::{OwaError, OwaValue, Scope, except_arity};
+
+static LIBRARIES: OnceLock<Mutex<HashMap<String, Library>>> = OnceLock::new();
+
+fn libraries() -> &'static Mutex<HashMap<String, Library>> {
+    LIBRARIES.get_or_init(|| Mutex::new(HashMap::new()))
+}
+
+fn runtime_err(msg: impl AsRef<str>) -> OwaError {
+    OwaError::RuntimeError(OwaValue::str(msg.as_ref()))
+}
+
+fn kw_to_ffi_type(kw: &str) -> Result<Type, OwaError> {
+    Ok(match kw {
+        "void" => Type::void(),
+        "ptr" | "str" => Type::pointer(), // both are just pointers at the ABI level
+        "i8" => Type::i8(),
+        "i16" => Type::i16(),
+        "i32" => Type::i32(),
+        "i64" => Type::i64(),
+        "u8" => Type::u8(),
+        "u16" => Type::u16(),
+        "u32" => Type::u32(),
+        "u64" => Type::u64(),
+        "f32" => Type::f32(),
+        "f64" => Type::f64(),
+        _ => return Err(runtime_err(format!("Unknown FFI type keyword: :{kw}"))),
+    })
+}
+
+// libffi expects a pointer-to-argument for each arg (void**).  We box every
+// value so the address stays stable regardless of Vec reallocations.
+enum ArgBacking {
+    I8(Box<i8>),
+    I16(Box<i16>),
+    I32(Box<i32>),
+    I64(Box<i64>),
+    U8(Box<u8>),
+    U16(Box<u16>),
+    U32(Box<u32>),
+    U64(Box<u64>),
+    F32(Box<f32>),
+    F64(Box<f64>),
+    Ptr(Box<*const c_void>),
+    // _cstring keeps the allocation alive; ptr is a boxed *const c_char into it
+    Str {
+        _cstring: Box<CString>,
+        ptr: Box<*const c_char>,
+    },
+}
+
+impl ArgBacking {
+    fn to_ffi_arg(&self) -> Arg<'_> {
+        match self {
+            Self::I8(v) => Arg::new(v.as_ref()),
+            Self::I16(v) => Arg::new(v.as_ref()),
+            Self::I32(v) => Arg::new(v.as_ref()),
+            Self::I64(v) => Arg::new(v.as_ref()),
+            Self::U8(v) => Arg::new(v.as_ref()),
+            Self::U16(v) => Arg::new(v.as_ref()),
+            Self::U32(v) => Arg::new(v.as_ref()),
+            Self::U64(v) => Arg::new(v.as_ref()),
+            Self::F32(v) => Arg::new(v.as_ref()),
+            Self::F64(v) => Arg::new(v.as_ref()),
+            Self::Ptr(p) => Arg::new(p.as_ref()),
+            Self::Str { ptr, .. } => Arg::new(ptr.as_ref()),
+        }
+    }
+}
+
+#[allow(clippy::cast_precision_loss)]
+fn prepare_backing(type_kw: &str, value: &OwaValue) -> Result<ArgBacking, OwaError> {
+    Ok(match type_kw {
+        "i8" => ArgBacking::I8(Box::new(value.as_int()? as i8)),
+        "i16" => ArgBacking::I16(Box::new(value.as_int()? as i16)),
+        "i32" => ArgBacking::I32(Box::new(value.as_int()? as i32)),
+        "i64" => ArgBacking::I64(Box::new(value.as_int()?)),
+        "u8" => ArgBacking::U8(Box::new(value.as_int()? as u8)),
+        "u16" => ArgBacking::U16(Box::new(value.as_int()? as u16)),
+        "u32" => ArgBacking::U32(Box::new(value.as_int()? as u32)),
+        "u64" => ArgBacking::U64(Box::new(value.as_int()? as u64)),
+        "f32" => {
+            let v = match value {
+                OwaValue::Float(f) => f.0 as f32,
+                OwaValue::Int(i) => *i as f32,
+                _ => {
+                    return Err(OwaError::TypeError(
+                        "float or int".into(),
+                        value.type_name().into(),
+                    ));
+                }
+            };
+            ArgBacking::F32(Box::new(v))
+        }
+        "f64" => {
+            let v = match value {
+                OwaValue::Float(f) => f.0,
+                OwaValue::Int(i) => *i as f64,
+                _ => {
+                    return Err(OwaError::TypeError(
+                        "float or int".into(),
+                        value.type_name().into(),
+                    ));
+                }
+            };
+            ArgBacking::F64(Box::new(v))
+        }
+        "ptr" => {
+            let raw = value.as_int()? as *const c_void;
+            ArgBacking::Ptr(Box::new(raw))
+        }
+        "str" => {
+            let s = value.as_str()?;
+            let cstring = Box::new(
+                CString::new(s.as_bytes())
+                    .map_err(|e| runtime_err(format!("Invalid string for FFI: {e}")))?,
+            );
+            // box the pointer separately so libffi can dereference it once
+            let ptr = Box::new(cstring.as_ptr());
+            ArgBacking::Str {
+                _cstring: cstring,
+                ptr,
+            }
+        }
+        _ => return Err(runtime_err(format!("Unknown FFI type keyword: :{type_kw}"))),
+    })
+}
+
+// # Safety: caller must ensure func_ptr matches the cif signature
+#[allow(clippy::cast_lossless, clippy::cast_possible_wrap)]
+unsafe fn dispatch_call(
+    cif: &Cif,
+    func_ptr: CodePtr,
+    ffi_args: &[Arg<'_>],
+    return_type: &str,
+) -> Result<OwaValue, OwaError> {
+    Ok(match return_type {
+        "void" => {
+            // libffi doesn't write the return slot for FFI_TYPE_VOID, so () is fine
+            unsafe { cif.call::<()>(func_ptr, ffi_args) };
+            OwaValue::int(0)
+        }
+        "i8" => OwaValue::int(unsafe { cif.call::<i8>(func_ptr, ffi_args) } as i64),
+        "i16" => OwaValue::int(unsafe { cif.call::<i16>(func_ptr, ffi_args) } as i64),
+        "i32" => OwaValue::int(unsafe { cif.call::<i32>(func_ptr, ffi_args) } as i64),
+        "i64" => OwaValue::int(unsafe { cif.call::<i64>(func_ptr, ffi_args) }),
+        "u8" => OwaValue::int(unsafe { cif.call::<u8>(func_ptr, ffi_args) } as i64),
+        "u16" => OwaValue::int(unsafe { cif.call::<u16>(func_ptr, ffi_args) } as i64),
+        "u32" => OwaValue::int(unsafe { cif.call::<u32>(func_ptr, ffi_args) } as i64),
+        "u64" => OwaValue::int(unsafe { cif.call::<u64>(func_ptr, ffi_args) } as i64),
+        "f32" => OwaValue::float(unsafe { cif.call::<f32>(func_ptr, ffi_args) } as f64),
+        "f64" => OwaValue::float(unsafe { cif.call::<f64>(func_ptr, ffi_args) }),
+        "ptr" => OwaValue::int(unsafe { cif.call::<usize>(func_ptr, ffi_args) } as i64),
+        "str" => {
+            let raw = unsafe { cif.call::<*const c_char>(func_ptr, ffi_args) };
+            if raw.is_null() {
+                OwaValue::str("")
+            } else {
+                let cstr = unsafe { CStr::from_ptr(raw) };
+                OwaValue::str(cstr.to_string_lossy().as_ref())
+            }
+        }
+        _ => {
+            return Err(runtime_err(format!(
+                "Unknown FFI return type: :{return_type}"
+            )));
+        }
+    })
+}
+
+#[must_use]
+pub fn owa_load() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [libname] = except_arity(args)?;
+        let libname = libname.clone();
+        let libname_str = libname.as_str()?;
+
+        if libraries()
+            .lock()
+            .map_err(|_| runtime_err("Failed to acquire library registry lock"))?
+            .contains_key(libname_str.as_ref())
+        {
+            return Ok(libname.into());
+        }
+
+        // Load the library without holding the lock to avoid unnecessary contention
+        let lib = unsafe {
+            Library::new(libname_str.as_ref())
+                .map_err(|e| runtime_err(format!("Failed to load '{libname_str}': {e}")))?
+        };
+
+        libraries()
+            .lock()
+            .map_err(|_| runtime_err("Failed to acquire library registry lock"))?
+            .insert(libname_str.to_string(), lib);
+        Ok(libname.into())
+    })
+}
+
+#[must_use]
+pub fn owa_unload() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [libname] = except_arity(args)?;
+        let libname = libname.clone();
+        let libname_str = libname.as_str()?;
+
+        libraries()
+            .lock()
+            .map_err(|_| runtime_err("Failed to acquire library registry lock"))?
+            .remove(libname_str.as_ref());
+        Ok(libname.into())
+    })
+}
+
+// (ffi.call libname funcname [[param-type ...] return-type] [args ...])
+//
+// Supported types: :void :ptr :str :i8 :i16 :i32 :i64 :u8 :u16 :u32 :u64 :f32 :f64
+// :str  — takes OwaValue::Str, passes const char*
+// :ptr  — takes OwaValue::Int as a raw address
+#[must_use]
+pub fn owa_call() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [libname, funcname, signature, call_args] = except_arity(args)?;
+        let libname = libname.as_str()?;
+        let funcname = funcname.as_str()?;
+        let signature = signature.as_vec()?;
+        let call_args = call_args.as_vec()?;
+
+        if signature.len() != 2 {
+            return Err(runtime_err(
+                "Signature must be [[param-type ...] return-type]",
+            ));
+        }
+        let param_types: Vec<_> = signature[0]
+            .as_vec()?
+            .iter()
+            .map(OwaValue::as_kw)
+            .collect::<Result<_, _>>()?;
+        let return_type = signature[1].as_kw()?;
+
+        if param_types.len() != call_args.len() {
+            return Err(OwaError::ArityError(param_types.len(), call_args.len()));
+        }
+
+        let ffi_param_types: Vec<Type> = param_types
+            .iter()
+            .map(|kw| kw_to_ffi_type(kw.as_ref()))
+            .collect::<Result<_, _>>()?;
+        let cif = Cif::new(ffi_param_types, kw_to_ffi_type(return_type.as_ref())?);
+
+        // grab the fn pointer while holding the lock, then release before calling
+        let func_ptr: CodePtr = unsafe {
+            let libs = libraries()
+                .lock()
+                .map_err(|_| runtime_err("Failed to acquire library registry lock"))?;
+            let ptr = {
+                let sym: libloading::Symbol<unsafe extern "C" fn()> = libs
+                    .get(libname.as_ref())
+                    .ok_or_else(|| runtime_err(format!("Library not loaded: '{libname}'")))?
+                    .get(funcname.as_bytes())
+                    .map_err(|e| {
+                        runtime_err(format!("Symbol '{funcname}' not found in '{libname}': {e}"))
+                    })?;
+                // fn ptr -> usize -> *mut c_void is the portable cast in Rust
+                CodePtr(*sym as usize as *mut c_void)
+            }; // sym (and its borrow of libs) dropped here
+            drop(libs);
+            ptr
+        };
+
+        let backings: Vec<ArgBacking> = param_types
+            .iter()
+            .zip(call_args.iter())
+            .map(|(kw, val)| prepare_backing(kw.as_ref(), val))
+            .collect::<Result<_, _>>()?;
+
+        let ffi_args: Vec<Arg<'_>> = backings.iter().map(ArgBacking::to_ffi_arg).collect();
+
+        unsafe { dispatch_call(&cif, func_ptr, &ffi_args, return_type.as_ref()) }.map(Into::into)
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("load", owa_load()),
+        ("unload", owa_unload()),
+        ("call", owa_call()),
+    ])
+}
diff --git a/src/builtins/flow.rs b/src/builtins/flow.rs
new file mode 100644
index 0000000..8845df9
--- /dev/null
+++ b/src/builtins/flow.rs
@@ -0,0 +1,51 @@
+use crate::core::{Completion, OwaError, OwaValue, Scope, special_names};
+
+#[must_use]
+pub fn owa_break() -> OwaValue {
+    OwaValue::native_function(|_, _, _| Ok(Completion::Break))
+}
+
+#[must_use]
+pub fn owa_continue() -> OwaValue {
+    OwaValue::native_function(|_, _, _| Ok(Completion::Continue))
+}
+
+#[must_use]
+pub fn owa_return() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        args.first().map_or_else(
+            || Err(OwaError::ArityMinError(1, 0)),
+            |result| Ok(Completion::Return(result.clone())),
+        )
+    })
+}
+
+#[must_use]
+pub fn owa_loop() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        'outer: loop {
+            for arg in args {
+                // Normalise both signal channels: Ok(Completion::*) from direct
+                // calls and Err(Signal(...)) from nested argument evaluation.
+                match Completion::from_result(interpreter.eval(arg, scope_id))? {
+                    Completion::Value(_) => {}
+                    Completion::Break => break 'outer,
+                    Completion::Continue => continue 'outer,
+                    Completion::Return(v) => return Ok(Completion::Value(v)),
+                }
+            }
+        }
+
+        Ok(OwaValue::kw(special_names::KW_NULL).into())
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("break", owa_break()),
+        ("continue", owa_continue()),
+        ("return", owa_return()),
+        ("loop", owa_loop()),
+    ])
+}
diff --git a/src/builtins/map.rs b/src/builtins/map.rs
new file mode 100644
index 0000000..29d6f66
--- /dev/null
+++ b/src/builtins/map.rs
@@ -0,0 +1,14 @@
+use crate::core::{OwaValue, Scope};
+
+#[must_use]
+pub fn owa_map() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let value = OwaValue::map(args.iter().cloned());
+        Ok(value.into())
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([("new", owa_map())])
+}
diff --git a/src/builtins/math.rs b/src/builtins/math.rs
new file mode 100644
index 0000000..029e873
--- /dev/null
+++ b/src/builtins/math.rs
@@ -0,0 +1,83 @@
+#![allow(clippy::cast_precision_loss)]
+use crate::core::{OwaError, OwaValue, Scope, except_arity};
+
+macro_rules! math_binary_op {
+    ($fn_name:ident, $int_op:tt, $float_op:tt) => {
+        #[must_use]
+        pub fn $fn_name() -> OwaValue {
+            OwaValue::native_function(|_, _, args: &[OwaValue]| {
+                match args {
+                    [arg] => {
+                        match (arg) {
+                            OwaValue::Int(a) => Ok(OwaValue::Int(0 $int_op a).into()),
+                            OwaValue::Float(a) => Ok(OwaValue::float(0.0 $float_op a.as_ref()).into()),
+                            _ => Err(OwaError::TypeError("number".into(), arg.type_name().into())),
+                        }
+                    },
+                    [first, rest @ ..] => {
+                        let mut first = first.clone();
+                        for arg in rest {
+                            first = match (&first, arg) {
+                                (OwaValue::Int(a), OwaValue::Int(b)) => OwaValue::Int(*a $int_op b),
+                                (OwaValue::Float(a), OwaValue::Float(b)) => OwaValue::Float(*a $float_op b),
+                                (OwaValue::Int(a), OwaValue::Float(b)) => OwaValue::float((*a as f64) $float_op b.as_ref()),
+                                (OwaValue::Float(a), OwaValue::Int(b)) => OwaValue::Float(*a $float_op (*b as f64)),
+                                _ => return Err(OwaError::TypeError("number".into(), arg.type_name().into())),
+                            }
+                        };
+                        Ok(first.into())
+                    },
+                    _ => Err(OwaError::ArityMinError(1, args.len())),
+                }
+            })
+        }
+    };
+}
+
+macro_rules! math_binary_op_method {
+    ($fn_name:ident, $int_method:ident, $float_method:ident) => {
+        #[must_use]
+        pub fn $fn_name() -> OwaValue {
+            OwaValue::native_function(|_, _, args: &[OwaValue]| {
+                let [value1, value2] = except_arity(args)?;
+                match (value1, value2) {
+                    (OwaValue::Int(a), OwaValue::Int(b)) => {
+                        Ok(OwaValue::Int(a.pow((*b).try_into().unwrap_or(0))).into())
+                    }
+                    (OwaValue::Float(a), OwaValue::Float(b)) => {
+                        Ok(OwaValue::float(a.powf(**b)).into())
+                    }
+                    (OwaValue::Int(a), OwaValue::Float(b)) => {
+                        Ok(OwaValue::float((*a as f64).powf(**b)).into())
+                    }
+                    (OwaValue::Float(a), OwaValue::Int(b)) => {
+                        Ok(OwaValue::float(a.powf(*b as f64)).into())
+                    }
+                    _ => Err(OwaError::TypeError(
+                        "number".into(),
+                        value1.type_name().into(),
+                    )),
+                }
+            })
+        }
+    };
+}
+
+math_binary_op!(owa_add, +, +);
+math_binary_op!(owa_sub, -, -);
+math_binary_op!(owa_mul, *, *);
+math_binary_op!(owa_div, /, /);
+math_binary_op!(owa_mod, %, %);
+math_binary_op_method!(owa_pow, pow, powf);
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("add", owa_add()),
+        ("sub", owa_sub()),
+        ("mul", owa_mul()),
+        ("div", owa_div()),
+        ("mod", owa_mod()),
+        ("pow", owa_pow()),
+    ])
+}
diff --git a/src/builtins/mod.rs b/src/builtins/mod.rs
new file mode 100644
index 0000000..9116b47
--- /dev/null
+++ b/src/builtins/mod.rs
@@ -0,0 +1,324 @@
+use std::sync::Arc;
+
+use rpds::VectorSync;
+
+use crate::{
+    core::{Completion, Interpreter, OwaError, OwaValue, Scope, except_arity, except_arity_min},
+    parser::ast::OwaAst,
+};
+
+pub mod ast;
+pub mod cond;
+pub mod errors;
+pub mod ffi;
+pub mod flow;
+pub mod map;
+pub mod math;
+pub mod platform;
+pub mod set;
+pub mod str;
+pub mod vec;
+
+#[must_use]
+pub fn owa_apply() -> OwaValue {
+    OwaValue::native_function(|interpreter, _, args| {
+        let ([first], rest) = except_arity_min(args)?;
+        let calle = first.as_callable()?;
+        let mut flat_args: Vec<OwaValue> = Vec::with_capacity(args.len());
+        for arg in rest {
+            match arg {
+                OwaValue::Vec(vec) => flat_args.extend(vec.iter().cloned()),
+                _ => flat_args.push(arg.clone()),
+            }
+        }
+        calle.call(interpreter, flat_args.as_slice())
+    })
+}
+
+#[must_use]
+pub fn owa_cmp() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [left, right] = except_arity(args)?;
+        let result = match left.cmp(right) {
+            std::cmp::Ordering::Less => OwaValue::int(-1),
+            std::cmp::Ordering::Equal => OwaValue::int(0),
+            std::cmp::Ordering::Greater => OwaValue::int(1),
+        };
+        Ok(result.into())
+    })
+}
+
+/// Returns a tuple of names and values
+///
+/// # Errors
+///
+/// Returns [`OwaError::TypeError`] if `names_ast` or `values_ast` are not the expected types
+pub fn get_names_and_values(
+    interpreter: &mut Interpreter,
+    scope_id: usize,
+    names_ast: &OwaAst,
+    values_ast: &OwaAst,
+) -> Result<(Vec<String>, Vec<OwaValue>), OwaError> {
+    let names = match names_ast {
+        OwaAst::Symbol(v) | OwaAst::Str(v) | OwaAst::Keyword(v) => vec![v.to_string()],
+        OwaAst::Vec(v) => v
+            .iter()
+            .map(super::parser::ast::OwaAst::to_sym)
+            .collect::<Result<_, _>>()?,
+        _ => {
+            let result = interpreter.eval_value(names_ast, scope_id)?;
+            let result = result.to_sym()?;
+            vec![result.to_string()]
+        }
+    };
+
+    let values = if names.len() == 1 {
+        vec![interpreter.eval_value(values_ast, scope_id)?]
+    } else {
+        let result = interpreter.eval_value(values_ast, scope_id)?;
+        let result = result.as_vec()?;
+        result.iter().cloned().collect()
+    };
+
+    Ok((names, values))
+}
+
+#[must_use]
+pub fn owa_def() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [key, value_ast] = except_arity(args)?;
+
+        let (names, values) = get_names_and_values(interpreter, scope_id, key, value_ast)?;
+        for (name, value) in names.iter().zip(values.iter()) {
+            interpreter.define_runtime(scope_id, name, value.clone())?;
+        }
+
+        if names.len() == 1 && values.len() == 1 {
+            Ok(values[0].clone().into())
+        } else {
+            Ok(OwaValue::vec(values).into())
+        }
+    })
+}
+
+#[must_use]
+pub fn owa_exec() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [variables_ast, bootstrap_ast, target] = except_arity(args)?;
+        let variables = interpreter.eval_value(variables_ast, scope_id)?;
+        let variables = variables.as_map()?;
+        let target = interpreter.eval_value(target, scope_id)?.as_str()?;
+
+        // create temp scope
+        let temp_scope_id = interpreter.inherit_scope(scope_id)?;
+
+        // load shared
+        for (key, value) in variables {
+            let key = &key.to_sym()?;
+            let value = value.clone();
+            interpreter.define_runtime(temp_scope_id, key, value)?;
+        }
+
+        // eval bootstrap
+        interpreter.eval_value(bootstrap_ast, temp_scope_id)?;
+
+        // isolate scope
+        let mut temp_scope = interpreter.get_scope_cloned(temp_scope_id)?;
+        temp_scope.parent = None;
+        temp_scope.token = std::sync::Arc::new(());
+        temp_scope.child_count = 0;
+        let isolated_scope_id = interpreter.allocate_scope(temp_scope)?;
+
+        // release temp scope (no longer needed after cloning)
+        interpreter.try_release_scope(temp_scope_id);
+
+        // eval
+        interpreter.run(target.as_ref(), isolated_scope_id)?;
+        let result = interpreter.get_scope_as_map(isolated_scope_id)?;
+        Ok(result.into())
+    })
+}
+
+#[must_use]
+pub fn owa_include() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [raw_filename] = except_arity(args)?;
+        let raw_filename = interpreter.eval_value(raw_filename, scope_id)?;
+        let raw_filename = raw_filename.as_str()?;
+        interpreter
+            .run(raw_filename.as_ref(), scope_id)
+            .map(Into::into)
+    })
+}
+
+#[must_use]
+pub fn owa_lambda() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [params, body] = except_arity(args)?;
+        let params = params.as_vec()?;
+        let params = params
+            .iter()
+            .map(OwaAst::as_sym)
+            .collect::<Result<VectorSync<_>, _>>()?;
+
+        let token = interpreter.get_scope_token(scope_id)?;
+        let value = OwaValue::new_lambda(body.clone(), params, scope_id, token);
+        Ok(value.into())
+    })
+}
+
+#[must_use]
+pub fn owa_lookup() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let ([key], rest) = except_arity_min(args)?;
+        let key = key.as_sym().or_else(|_| {
+            let result = interpreter
+                .eval_value(&args[0], scope_id)
+                .map(|v| v.unparse())?;
+            Ok(Arc::from(result.as_str()))
+        })?;
+        let default = rest.first();
+
+        let value = interpreter.lookup_runtime(scope_id, &key);
+        match value {
+            Ok(v) => Ok(v.clone().into()),
+            Err(e) => default.map_or_else(
+                || Err(e),
+                |default| interpreter.eval_value(default, scope_id).map(Into::into),
+            ),
+        }
+    })
+}
+
+#[must_use]
+pub fn owa_macro() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [params, body] = except_arity(args)?;
+        let params = params.as_vec()?;
+
+        let params = params
+            .iter()
+            .map(OwaAst::as_sym)
+            .collect::<Result<VectorSync<_>, _>>()?;
+
+        let token = interpreter.get_scope_token(scope_id)?;
+        let value = OwaValue::new_macro(body.clone(), params, scope_id, token);
+        Ok(value.into())
+    })
+}
+
+#[must_use]
+pub fn owa_trace() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        for arg in args {
+            match arg {
+                OwaValue::Str(v) => print!("{v}"),
+                _ => print!("{}", arg.unparse()),
+            }
+        }
+        println!();
+        Ok(OwaValue::str("").into())
+    })
+}
+
+#[must_use]
+pub fn owa_typeof() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let [value] = except_arity(args)?;
+        Ok(OwaValue::kw(value.type_name()).into())
+    })
+}
+
+#[must_use]
+pub fn owa_scope() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let inner_scope_id = interpreter.inherit_scope(scope_id)?;
+        let _ = interpreter.eval_collection::<_, Vec<_>>(args, inner_scope_id)?;
+        let inner_map = interpreter.get_scope_as_map(inner_scope_id)?;
+        interpreter.try_release_scope(inner_scope_id);
+        Ok(inner_map.into())
+    })
+}
+
+#[must_use]
+pub fn owa_set() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let [key, value_ast] = except_arity(args)?;
+
+        let (names, values) = get_names_and_values(interpreter, scope_id, key, value_ast)?;
+        for (name, value) in names.iter().zip(values.iter()) {
+            interpreter.set_runtime(scope_id, name, value.clone())?;
+        }
+
+        if names.len() == 1 && values.len() == 1 {
+            Ok(values[0].clone().into())
+        } else {
+            Ok(OwaValue::vec(values).into())
+        }
+    })
+}
+
+#[must_use]
+pub fn owa_unset() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let mut result = Vec::with_capacity(args.len());
+        for arg in args {
+            let value = interpreter.lookup_runtime(scope_id, &arg.to_str())?.clone();
+            interpreter.unset_runtime(scope_id, &arg.to_str())?;
+            result.push(value);
+        }
+        Ok(OwaValue::vec(result).into())
+    })
+}
+
+#[must_use]
+pub fn owa_seq() -> OwaValue {
+    OwaValue::native_macro(|interpreter, scope_id, args| {
+        let mut last = None;
+        for arg in args {
+            // Normalise both signal channels: Ok(Completion::*) from direct calls
+            // and Err(Signal(...)) from nested argument evaluation (e.g. inside
+            // a `namespace` / `scope` that uses eval_collection).
+            match Completion::from_result(interpreter.eval(arg, scope_id))? {
+                Completion::Value(v) => last = Some(v),
+                // Return is caught here — it exits the seq with the returned value
+                Completion::Return(v) => return Ok(Completion::Value(v)),
+                // Break/Continue propagate outward (they belong to an enclosing loop)
+                c => return Ok(c),
+            }
+        }
+        last.ok_or_else(|| OwaError::ArityMinError(1, args.len()))
+            .map(Completion::Value)
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("apply", owa_apply()),
+        ("cmp", owa_cmp()),
+        ("def", owa_def()),
+        ("exec", owa_exec()),
+        ("lambda", owa_lambda()),
+        ("lookup", owa_lookup()),
+        ("macro", owa_macro()),
+        ("trace", owa_trace()),
+        ("typeof", owa_typeof()),
+        ("include", owa_include()),
+        ("scope", owa_scope()),
+        ("set!", owa_set()),
+        ("unset!", owa_unset()),
+        ("seq", owa_seq()),
+        ("ast", ast::scope().local_runtime_to_map()),
+        ("cond", cond::scope().local_runtime_to_map()),
+        ("errors", errors::scope().local_runtime_to_map()),
+        ("ffi", ffi::scope().local_runtime_to_map()),
+        ("flow", flow::scope().local_runtime_to_map()),
+        ("map", map::scope().local_runtime_to_map()),
+        ("math", math::scope().local_runtime_to_map()),
+        ("platform", platform::scope().local_runtime_to_map()),
+        ("set", set::scope().local_runtime_to_map()),
+        ("str", str::scope().local_runtime_to_map()),
+        ("vec", vec::scope().local_runtime_to_map()),
+    ])
+}
diff --git a/src/builtins/platform.rs b/src/builtins/platform.rs
new file mode 100644
index 0000000..cd7bcec
--- /dev/null
+++ b/src/builtins/platform.rs
@@ -0,0 +1,19 @@
+use crate::core::{OwaValue, Scope};
+
+#[must_use]
+pub fn owa_argv() -> OwaValue {
+    OwaValue::native_function(|_, _, _| {
+        let args = std::env::args().map(OwaValue::str);
+        Ok(OwaValue::vec(args).into())
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("os-name", OwaValue::kw(std::env::consts::OS)),
+        ("os-family", OwaValue::kw(std::env::consts::FAMILY)),
+        ("arch", OwaValue::str(std::env::consts::ARCH)),
+        ("argv", owa_argv()),
+    ])
+}
diff --git a/src/builtins/set.rs b/src/builtins/set.rs
new file mode 100644
index 0000000..0306b82
--- /dev/null
+++ b/src/builtins/set.rs
@@ -0,0 +1,47 @@
+use crate::core::{Completion, OwaValue, Scope, except_arity};
+
+#[must_use]
+pub fn owa_set_from() -> OwaValue {
+    OwaValue::native_function(|_, _, args: &[OwaValue]| {
+        let mut elements = Vec::new();
+        for arg in args {
+            match arg {
+                OwaValue::Vec(values) => elements.extend(values.iter().cloned()),
+                OwaValue::Set(values) => elements.extend(values.iter().cloned()),
+                OwaValue::Map(values) => elements.extend(values.keys().cloned()),
+                OwaValue::Str(v) => {
+                    elements.extend(v.chars().map(|v| OwaValue::str(v.to_string())));
+                }
+                _ => elements.push(arg.clone()),
+            }
+        }
+        Ok(OwaValue::set(elements).into())
+    })
+}
+
+#[must_use]
+pub fn owa_fold() -> OwaValue {
+    OwaValue::native_function(|interpreter, _, args| {
+        let [lambda, initial, set] = except_arity(args)?;
+
+        let callable = lambda.as_callable()?;
+        let set = set.as_set()?;
+        let mut initial = initial.clone();
+
+        for value in set {
+            let call_args = [initial.clone(), value.clone()];
+            match Completion::from_result(callable.call(interpreter, &call_args))? {
+                Completion::Value(v) => initial = v,
+                Completion::Break => break,
+                Completion::Continue => continue,
+                Completion::Return(v) => return Ok(Completion::Value(v)),
+            }
+        }
+        Ok(initial.into())
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([("from", owa_set_from()), ("fold", owa_fold())])
+}
diff --git a/src/builtins/str.rs b/src/builtins/str.rs
new file mode 100644
index 0000000..64b012a
--- /dev/null
+++ b/src/builtins/str.rs
@@ -0,0 +1,48 @@
+use crate::core::{OwaValue, Scope};
+
+#[must_use]
+pub fn owa_to_str() -> OwaValue {
+    OwaValue::native_function(|_, _, args: &[OwaValue]| {
+        let value = OwaValue::str(
+            args.iter()
+                .map(|v| match v {
+                    OwaValue::Str(v) => v.to_string(),
+                    _ => v.unparse(),
+                })
+                .collect::<String>(),
+        );
+        Ok(value.into())
+    })
+}
+
+#[must_use]
+pub fn owa_to_kw() -> OwaValue {
+    OwaValue::native_function(|_, _, args: &[OwaValue]| {
+        let value = OwaValue::kw(
+            args.iter()
+                .map(|v| match v {
+                    OwaValue::Str(v) | OwaValue::Keyword(v) => v.to_string(),
+                    _ => v.unparse(),
+                })
+                .collect::<String>(),
+        );
+        Ok(value.into())
+    })
+}
+
+#[must_use]
+pub fn owa_serialize() -> OwaValue {
+    OwaValue::native_function(|_, _, args| {
+        let value = OwaValue::str(args.iter().map(OwaValue::unparse).collect::<String>());
+        Ok(value.into())
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("new", owa_to_str()),
+        ("kw", owa_to_kw()),
+        ("serialize", owa_serialize()),
+    ])
+}
diff --git a/src/builtins/vec.rs b/src/builtins/vec.rs
new file mode 100644
index 0000000..472b6ba
--- /dev/null
+++ b/src/builtins/vec.rs
@@ -0,0 +1,66 @@
+use crate::core::{Completion, OwaValue, Scope, except_arity};
+
+#[must_use]
+pub fn owa_vec_new() -> OwaValue {
+    OwaValue::native_function(|_, _, args: &[OwaValue]| {
+        let value = OwaValue::vec(args.iter().cloned());
+        Ok(value.into())
+    })
+}
+
+#[must_use]
+pub fn owa_vec_from() -> OwaValue {
+    OwaValue::native_function(|_, _, args: &[OwaValue]| {
+        let mut result = Vec::with_capacity(args.len());
+        for arg in args {
+            match arg {
+                OwaValue::Vec(values) => result.extend(values.iter().cloned()),
+                OwaValue::Set(values) => result.extend(values.iter().cloned()),
+                OwaValue::Map(values) => {
+                    result.extend(
+                        values
+                            .iter()
+                            .map(|(k, v)| OwaValue::vec([k.clone(), v.clone()])),
+                    );
+                }
+                OwaValue::Str(v) => result.extend(v.chars().map(|v| OwaValue::str(v.to_string()))),
+                _ => result.push(arg.clone()),
+            }
+        }
+        Ok(OwaValue::vec(result).into())
+    })
+}
+
+#[must_use]
+pub fn owa_fold() -> OwaValue {
+    OwaValue::native_function(|interpreter, _, args| {
+        let [lambda, initial, vector] = except_arity(args)?;
+
+        let callable = lambda.as_callable()?;
+        let vector = vector.as_vec()?;
+        let mut acc = initial.clone();
+        let mut call_args = [OwaValue::Int(0), OwaValue::Int(0), OwaValue::Int(0)];
+
+        for (idx, value) in vector.iter().enumerate() {
+            call_args[0] = std::mem::replace(&mut acc, OwaValue::Int(0));
+            call_args[1] = value.clone();
+            call_args[2] = OwaValue::int(idx);
+            match Completion::from_result(callable.call(interpreter, &call_args))? {
+                Completion::Value(v) => acc = v,
+                Completion::Break => break,
+                Completion::Continue => continue,
+                Completion::Return(v) => return Ok(Completion::Value(v)),
+            }
+        }
+        Ok(acc.into())
+    })
+}
+
+#[must_use]
+pub fn scope() -> Scope {
+    Scope::new_with_runtime([
+        ("new", owa_vec_new()),
+        ("from", owa_vec_from()),
+        ("fold", owa_fold()),
+    ])
+}
diff --git a/src/core/callable.rs b/src/core/callable.rs
new file mode 100644
index 0000000..ed50c01
--- /dev/null
+++ b/src/core/callable.rs
@@ -0,0 +1,234 @@
+#![allow(unpredictable_function_pointer_comparisons)]
+use std::{hash::Hash, sync::Arc};
+
+use educe::Educe;
+use rpds::VectorSync;
+use tracing::debug;
+
+use crate::{
+    core::{Completion, Interpreter, OwaError, OwaValue, ScopeId, special_names},
+    parser::ast::{Expander, OwaAst},
+    vec_unparse,
+};
+
+pub type OwaNativeFunction =
+    fn(&mut Interpreter, ScopeId, &[OwaValue]) -> Result<Completion, OwaError>;
+pub type OwaNativeMacro = fn(&mut Interpreter, ScopeId, &[OwaAst]) -> Result<Completion, OwaError>;
+
+#[derive(Debug, Hash, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub enum OwaCallableCell {
+    NativeLambda(OwaNativeFunction),
+    NativeMacro(OwaNativeMacro),
+    Lambda(Arc<OwaAst>),
+    Macro(Arc<OwaAst>),
+}
+
+#[derive(Educe)]
+#[educe(Debug, Hash, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub struct OwaCallable {
+    #[educe(Debug(ignore), Hash(ignore), PartialEq(ignore), PartialOrd(ignore))]
+    pub scope_id: ScopeId,
+    #[educe(Debug(ignore), Hash(ignore), PartialEq(ignore), PartialOrd(ignore))]
+    pub scope_token: Arc<()>,
+    pub params: VectorSync<Arc<str>>,
+    pub body: OwaCallableCell,
+}
+
+impl OwaCallable {
+    fn call_macro<'a, I>(
+        &self,
+        interpreter: &mut Interpreter,
+        args: I,
+        scope_id: ScopeId,
+    ) -> Result<Completion, OwaError>
+    where
+        I: IntoIterator<Item = &'a OwaAst>,
+    {
+        // remove annotations
+        let args = args.into_iter().map(|a| a.unannotate()).collect::<Vec<_>>();
+
+        // check arity
+        if args.len() < self.params.len() {
+            return Err(OwaError::ArityError(self.params.len(), args.len()));
+        }
+
+        // create call scope
+        self.load_expand_args(interpreter, scope_id, &args)?;
+
+        match &self.body {
+            OwaCallableCell::NativeMacro(native) => native(interpreter, scope_id, &args),
+            OwaCallableCell::Macro(body) => {
+                let expanded = Expander::new(interpreter, scope_id).expand(body, false, false);
+                debug!("expanded: {expanded:?}");
+                interpreter.eval(&expanded, scope_id)
+            }
+            _ => Err(OwaError::TypeError("macro".into(), self.type_name().into())),
+        }
+    }
+
+    /// Calls this callable with the given pre-evaluated arguments.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::ArityError`] if too few arguments are provided.
+    /// Returns [`OwaError::TypeError`] if the body is not a lambda variant.
+    /// Propagates any error returned by the lambda body or native function.
+    pub fn call(
+        &self,
+        interpreter: &mut Interpreter,
+        args: &[OwaValue],
+    ) -> Result<Completion, OwaError> {
+        // check arity
+        if args.len() < self.params.len() {
+            return Err(OwaError::ArityError(self.params.len(), args.len()));
+        }
+
+        // create scope
+        let call_scope_id = interpreter.inherit_scope(self.scope_id)?;
+        self.load_args(interpreter, call_scope_id, args)?;
+
+        // eval
+        let result = match &self.body {
+            OwaCallableCell::Lambda(body) => interpreter.eval(body, call_scope_id),
+            OwaCallableCell::NativeLambda(native) => native(interpreter, call_scope_id, args),
+            _ => Err(OwaError::TypeError(
+                "lambda".into(),
+                self.type_name().into(),
+            )),
+        };
+
+        interpreter.try_release_scope(call_scope_id);
+        result
+    }
+
+    /// Evaluates the callable with the given raw AST arguments.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError`] if argument evaluation or the underlying call fails.
+    pub fn eval<'a, I>(
+        &self,
+        interpreter: &mut Interpreter,
+        raw_args: I,
+        scope_id: ScopeId,
+    ) -> Result<Completion, OwaError>
+    where
+        I: IntoIterator<Item = &'a OwaAst>,
+    {
+        match &self.body {
+            OwaCallableCell::NativeMacro(_) | OwaCallableCell::Macro(_) => {
+                self.call_macro(interpreter, raw_args, scope_id)
+            }
+            OwaCallableCell::NativeLambda(_) | OwaCallableCell::Lambda(_) => {
+                let args: Vec<OwaValue> = interpreter.eval_collection(raw_args, scope_id)?;
+                self.call(interpreter, &args)
+            }
+        }
+    }
+
+    /// Defines all call arguments (`this`, `%%`, `%&`, named params, indexed params)
+    /// in the given scope.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if any variable is already defined in the scope.
+    #[allow(clippy::needless_pass_by_value)]
+    fn load_args(
+        &self,
+        interpreter: &mut Interpreter,
+        scope_id: ScopeId,
+        args: &[OwaValue],
+    ) -> Result<(), OwaError> {
+        // define self
+        interpreter.define_runtime(
+            scope_id,
+            special_names::THIS_CALLABLE,
+            OwaValue::Callable(self.clone()),
+        )?;
+
+        // define special arguments
+        interpreter.define_runtime(
+            scope_id,
+            special_names::ALL_ARGS,
+            OwaValue::vec(args.iter().cloned()),
+        )?;
+        interpreter.define_runtime(
+            scope_id,
+            special_names::REST_ARGS,
+            OwaValue::vec(args.iter().skip(self.params.len()).cloned()),
+        )?;
+
+        // define named arguments
+        for (idx, param) in self.params.iter().enumerate() {
+            interpreter.define_runtime(scope_id, param, args[idx].clone())?;
+        }
+
+        // define indexed arguments
+        for (idx, arg) in args.iter().enumerate() {
+            interpreter.define_runtime(scope_id, &format!("%{}", idx + 1), arg.clone())?;
+        }
+
+        Ok(())
+    }
+
+    #[allow(clippy::needless_pass_by_value)]
+    fn load_expand_args(
+        &self,
+        interpreter: &mut Interpreter,
+        scope_id: ScopeId,
+        args: &[OwaAst],
+    ) -> Result<(), OwaError> {
+        // define special arguments
+        interpreter.set_expand(
+            scope_id,
+            special_names::ALL_ARGS,
+            OwaAst::vec(args.iter().cloned()),
+        )?;
+        interpreter.set_expand(
+            scope_id,
+            special_names::REST_ARGS,
+            OwaAst::vec(args.iter().skip(self.params.len()).cloned()),
+        )?;
+
+        // define named arguments
+        for (idx, param) in self.params.iter().enumerate() {
+            interpreter.set_expand(scope_id, param, args[idx].clone())?;
+        }
+
+        // define indexed arguments
+        for (idx, arg) in args.iter().enumerate() {
+            interpreter.set_expand(scope_id, &format!("%{}", idx + 1), arg.clone())?;
+        }
+
+        Ok(())
+    }
+
+    #[must_use]
+    pub fn get_param_index(&self, name: &str) -> Option<usize> {
+        self.params.iter().position(|p| p.clone().as_ref() == name)
+    }
+
+    #[must_use]
+    pub const fn type_name(&self) -> &'static str {
+        match self.body {
+            OwaCallableCell::NativeLambda(_) | OwaCallableCell::Lambda(_) => "lambda",
+            OwaCallableCell::NativeMacro(_) | OwaCallableCell::Macro(_) => "macro",
+        }
+    }
+
+    #[must_use]
+    pub fn unparse(&self) -> String {
+        match &self.body {
+            OwaCallableCell::Lambda(v) => match v.as_ref() {
+                OwaAst::Call(items) => format!("#{}", vec_unparse!(items.iter())),
+                _ => format!("#({})", v.unparse()),
+            },
+            OwaCallableCell::NativeLambda(_) => "#(!native.lambda!)".to_string(),
+            OwaCallableCell::Macro(v) => match v.as_ref() {
+                OwaAst::Call(items) => format!("#{}", vec_unparse!(items.iter())),
+                _ => format!("@({})", v.unparse()),
+            },
+            OwaCallableCell::NativeMacro(_) => "#(!native.macro!)".to_string(),
+        }
+    }
+}
diff --git a/src/core/error.rs b/src/core/error.rs
new file mode 100644
index 0000000..9e73960
--- /dev/null
+++ b/src/core/error.rs
@@ -0,0 +1,207 @@
+use crate::core::OwaValue;
+
+/// Payload carried by `break`, `continue`, and `return` signals.
+///
+/// This is kept separate from [`OwaError`] so that control flow can travel
+/// through two independent channels:
+///
+/// * **`Ok(Completion::*)`** — produced directly by the `break`/`continue`/
+///   `return` native functions and propagated through `eval`/`callable::call`.
+/// * **`Err(OwaError::Signal(...))`** — produced when a signal passes through
+///   a value-evaluation context (e.g. argument lists via `eval_collection`).
+///   This mirrors the old viral-error propagation so that constructs like
+///   `(for x v (continue))` still work correctly even though the `continue`
+///   originates inside a nested lambda.
+///
+/// Both channels are unified by [`Completion::from_result`].
+#[derive(Debug, Hash, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub enum FlowOperation {
+    Break,
+    Continue,
+    Return(OwaValue),
+}
+
+/// Represents the outcome of evaluating an expression.
+///
+/// Normal expressions produce `Value`. Control-flow constructs (`break`,
+/// `continue`, `return`) produce the corresponding variant. These are NOT
+/// errors — they are intentional signals that loops and sequences catch.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum Completion {
+    /// The expression evaluated to a value normally.
+    Value(OwaValue),
+    /// A `break` signal was emitted.
+    Break,
+    /// A `continue` signal was emitted.
+    Continue,
+    /// A `return` signal was emitted with its return value.
+    Return(OwaValue),
+}
+
+impl Completion {
+    /// Normalises a result by converting `OwaError::Signal` errors back into
+    /// `Completion` variants.
+    ///
+    /// Control-flow signals may travel via two channels:
+    /// * `Ok(Completion::Break/Continue/Return)` — from a direct lambda call.
+    /// * `Err(OwaError::Signal(...))` — from nested argument evaluation.
+    ///
+    /// Call this function wherever both channels must be handled (loops, seq).
+    ///
+    /// # Errors
+    ///
+    /// * `Ok(Completion::Value(v))` — the expression evaluated to a value normally.
+    /// * `Ok(Completion::Break/Continue/Return)` — a control-flow signal was emitted.
+    /// * `Err(OwaError::Panic(_))` — a `break` signal was emitted outside a loop.
+    pub fn from_result(result: Result<Self, OwaError>) -> Result<Self, OwaError> {
+        match result {
+            Err(OwaError::Signal(f)) => Ok(f.into()),
+            other => other,
+        }
+    }
+
+    /// Unwraps the inner value, converting control-flow signals into
+    /// user-visible panic errors.
+    ///
+    /// Use this only when control flow is genuinely unexpected (e.g. at the
+    /// top level of a file). Inside loops / sequences use [`from_result`] +
+    /// a pattern match instead.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if this is `Break`, `Continue`, or `Return`.
+    pub fn into_value(self) -> Result<OwaValue, OwaError> {
+        match self {
+            Self::Value(v) => Ok(v),
+            Self::Break => Err(OwaError::Panic("Unexpected break outside loop".into())),
+            Self::Continue => Err(OwaError::Panic("Unexpected continue outside loop".into())),
+            Self::Return(v) => Err(OwaError::Panic(format!(
+                "Unexpected return: {}",
+                v.unparse()
+            ))),
+        }
+    }
+}
+
+impl From<OwaValue> for Completion {
+    fn from(v: OwaValue) -> Self {
+        Self::Value(v)
+    }
+}
+
+impl From<FlowOperation> for Completion {
+    fn from(f: FlowOperation) -> Self {
+        match f {
+            FlowOperation::Break => Self::Break,
+            FlowOperation::Continue => Self::Continue,
+            FlowOperation::Return(v) => Self::Return(v),
+        }
+    }
+}
+
+#[derive(Debug, Hash, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub enum OwaError {
+    TypeError(String, String),                 // expected type A, got type B
+    ArityError(usize, usize),                  // expected N, got M
+    ArityMaxError(usize, usize),               // expected max N args, got M
+    ArityMinError(usize, usize),               // expected min N args, got M
+    InvalidMemberAccess(String, &'static str), // name A; type B
+    Panic(String),
+    EmptyCall,
+    RuntimeError(OwaValue),
+    UnboundVariable(String),
+    /// Internal: a control-flow signal propagating through value-evaluation
+    /// contexts (e.g. argument lists). Never shown to the user as a top-level
+    /// error; always caught by the nearest loop / sequence construct.
+    Signal(FlowOperation),
+}
+
+impl OwaError {
+    #[must_use]
+    pub const fn type_name(&self) -> &'static str {
+        match self {
+            Self::TypeError(_, _) => "TypeError",
+            Self::ArityError(_, _) => "ArityError",
+            Self::ArityMaxError(_, _) => "ArityMaxError",
+            Self::ArityMinError(_, _) => "ArityMinError",
+            Self::InvalidMemberAccess(_, _) => "InvalidMemberAccess",
+            Self::Panic(_) => "Panic",
+            Self::EmptyCall => "EmptyCall",
+            Self::RuntimeError(_) => "RuntimeError",
+            Self::UnboundVariable(_) => "UnboundVariable",
+            Self::Signal(_) => "Signal",
+        }
+    }
+
+    #[must_use]
+    pub fn message(&self) -> String {
+        match self {
+            Self::TypeError(expected, got) => {
+                format!("expected type {expected}, got type {got}")
+            }
+            Self::ArityError(expected, got) => {
+                format!("expected {expected} args, got {got}")
+            }
+            Self::ArityMaxError(max, got) => {
+                format!("expected max {max} args, got {got}")
+            }
+            Self::ArityMinError(min, got) => {
+                format!("expected min {min} args, got {got}")
+            }
+            Self::InvalidMemberAccess(name, type_name) => {
+                format!("cannot access member '{name}' on type {type_name}")
+            }
+            Self::Panic(message) => message.to_owned(),
+            Self::EmptyCall => "empty call".to_string(),
+            Self::RuntimeError(value) => format!("runtime error: {}", value.unparse()),
+            Self::UnboundVariable(name) => format!("unbound variable {name}"),
+            Self::Signal(FlowOperation::Break) => "break outside loop".to_string(),
+            Self::Signal(FlowOperation::Continue) => "continue outside loop".to_string(),
+            Self::Signal(FlowOperation::Return(v)) => {
+                format!("unexpected return: {}", v.unparse())
+            }
+        }
+    }
+}
+
+impl std::fmt::Display for OwaError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}: {}", self.type_name(), self.message())
+    }
+}
+
+/// Collects `args` into a fixed-size array of length `N`.
+///
+/// # Errors
+///
+/// Returns [`OwaError::ArityError`] if the number of items in `args` is not exactly `N`.
+pub fn except_arity<T: std::fmt::Debug, C, const N: usize>(args: C) -> Result<[T; N], OwaError>
+where
+    C: IntoIterator<Item = T>,
+{
+    let args = args.into_iter().collect::<Vec<_>>();
+    let len = args.len();
+    args.try_into().map_err(|_| OwaError::ArityError(N, len))
+}
+
+/// Collects `args` into a fixed-size array of length `N` or more,
+/// returning the fixed-size array and any remaining items as a [`Vec`].
+///
+/// # Errors
+///
+/// Returns [`OwaError::ArityMinError`] if the number of items in `args` is less than `N`.
+pub fn except_arity_min<T: std::fmt::Debug, C, const N: usize>(
+    args: C,
+) -> Result<([T; N], Vec<T>), OwaError>
+where
+    C: IntoIterator<Item = T>,
+{
+    let mut args = args.into_iter().collect::<Vec<_>>();
+    let len = args.len();
+    if len < N {
+        return Err(OwaError::ArityMinError(N, len));
+    }
+    let rest = args.split_off(N);
+    let fixed: [T; N] = args.try_into().map_err(|_| OwaError::ArityError(N, len))?;
+    Ok((fixed, rest))
+}
diff --git a/src/core/interpreter.rs b/src/core/interpreter.rs
new file mode 100644
index 0000000..c125ce3
--- /dev/null
+++ b/src/core/interpreter.rs
@@ -0,0 +1,492 @@
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use rpds::{RedBlackTreeMapSync, RedBlackTreeSetSync, VectorSync};
+use tracing::trace;
+
+use crate::{
+    core::{Completion, FlowOperation, OwaError, OwaValue, Scope, ScopeId, special_names},
+    parser::{ast::OwaAst, parse_file},
+};
+
+#[derive(Debug, Clone, Default)]
+pub struct Interpreter {
+    scopes: Vec<Option<Scope>>,
+    free_list: Vec<ScopeId>,
+    pub max_scopes_count: Option<usize>,
+}
+
+impl Interpreter {
+    pub const fn new(max_scopes_count: Option<usize>) -> Self {
+        Self {
+            scopes: Vec::new(),
+            free_list: Vec::new(),
+            max_scopes_count,
+        }
+    }
+
+    /// Resolves, parses and evaluates an OWA source file relative to the current
+    /// `__dir__` runtime variable.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::UnboundVariable`] if `__dir__` is not set in the scope.
+    /// Returns [`OwaError::Panic`] if the file cannot be found, read, or parsed.
+    /// Propagates any [`OwaError`] produced while evaluating the file.
+    pub fn run<S>(&mut self, filename: S, scope_id: ScopeId) -> Result<OwaValue, OwaError>
+    where
+        S: Into<String>,
+    {
+        // resolve
+        let olddir = self.lookup_runtime(scope_id, special_names::DIR)?.clone();
+        let filename: String = filename.into();
+        let filename_path = std::path::Path::new(olddir.as_str()?.as_ref()).join(&filename);
+        trace!("run {}", filename_path.display());
+        let filename_resolved = resolve_owa_path(&filename_path)
+            .ok_or_else(|| OwaError::Panic(format!("Could not find file {filename}")))?;
+
+        // parse
+        let ast = parse_file(&filename_resolved).map_err(OwaError::Panic)?;
+
+        // update __dir__
+        let dir = std::path::Path::new(&filename_resolved)
+            .parent()
+            .and_then(|p| p.to_str());
+
+        if let Some(dir) = dir {
+            self.set_runtime(scope_id, special_names::DIR, OwaValue::str(dir))?;
+        }
+
+        // eval — normalise both signal channels, then catch Return at the top level
+        let result = match Completion::from_result(self.eval(&ast, scope_id))? {
+            Completion::Value(v) | Completion::Return(v) => v,
+            Completion::Break => {
+                return Err(OwaError::Panic("Unexpected break at top level".into()));
+            }
+            Completion::Continue => {
+                return Err(OwaError::Panic("Unexpected continue at top level".into()));
+            }
+        };
+
+        // restore __dir__
+        self.set_runtime(scope_id, special_names::DIR, olddir)?;
+
+        Ok(result)
+    }
+
+    /// Evaluates a single AST node and returns a [`Completion`].
+    ///
+    /// Returns `Completion::Value` for normal expressions and
+    /// `Completion::Break`/`Continue`/`Return` for control-flow signals.
+    ///
+    /// # Errors
+    ///
+    /// Propagates any [`OwaError`] produced during evaluation.
+    pub fn eval(&mut self, value: &OwaAst, scope_id: ScopeId) -> Result<Completion, OwaError> {
+        trace!("scopes count: {}", self.scopes.len());
+        match value {
+            OwaAst::Symbol(v) => self.eval_symbol(v, scope_id).map(Completion::Value),
+            OwaAst::Keyword(v) => Ok(OwaValue::kw(v).into()),
+            OwaAst::Str(v) => Ok(OwaValue::str(v).into()),
+            OwaAst::Float(v) => Ok(OwaValue::Float(*v).into()),
+            OwaAst::Int(v) => Ok(OwaValue::Int(*v).into()),
+            OwaAst::Vec(v) => self.eval_vector(v, scope_id).map(Completion::Value),
+            OwaAst::Call(v) => self.eval_call(v, scope_id),
+            OwaAst::Set(v) => self.eval_set(v, scope_id).map(Completion::Value),
+            OwaAst::Map(v) => self.eval_map(v, scope_id).map(Completion::Value),
+            OwaAst::Quote(v) => Ok(OwaValue::quote(v.clone()).into()),
+            OwaAst::Unquote(v) => self.eval(v.as_ref(), scope_id),
+            OwaAst::Lambda(v) => {
+                let call = OwaAst::call(v.iter().cloned());
+                let token = self.get_scope_token(scope_id)?;
+                let lambda = OwaValue::new_lambda(call, VectorSync::default(), scope_id, token);
+                Ok(lambda.into())
+            }
+            OwaAst::Annotation(v) => self.eval(&v.value, scope_id),
+        }
+    }
+
+    /// Evaluates a single AST node and unwraps it to an [`OwaValue`].
+    ///
+    /// Control-flow signals (`Break`, `Continue`, `Return`) are converted to
+    /// [`OwaError::Signal`] so they propagate virally through argument
+    /// evaluation until the nearest loop / sequence catches them via
+    /// [`Completion::from_result`].
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Signal`] if the result is a control-flow signal.
+    /// Propagates any other [`OwaError`] produced during evaluation.
+    pub fn eval_value(&mut self, value: &OwaAst, scope_id: ScopeId) -> Result<OwaValue, OwaError> {
+        match self.eval(value, scope_id)? {
+            Completion::Value(v) => Ok(v),
+            Completion::Break => Err(OwaError::Signal(FlowOperation::Break)),
+            Completion::Continue => Err(OwaError::Signal(FlowOperation::Continue)),
+            Completion::Return(v) => Err(OwaError::Signal(FlowOperation::Return(v))),
+        }
+    }
+
+    fn eval_symbol(&self, symbol: &str, scope_id: ScopeId) -> Result<OwaValue, OwaError> {
+        // specials
+        if is_special_symbol(symbol) {
+            match symbol {
+                special_names::SCOPE => return self.get_scope_as_map(scope_id),
+                _ => (),
+            }
+        }
+
+        // normal
+        self.lookup_runtime(scope_id, symbol).cloned()
+    }
+
+    fn eval_vector(
+        &mut self,
+        value: &VectorSync<OwaAst>,
+        scope_id: ScopeId,
+    ) -> Result<OwaValue, OwaError> {
+        self.eval_collection(value, scope_id).map(OwaValue::Vec)
+    }
+
+    fn eval_call(
+        &mut self,
+        value: &VectorSync<OwaAst>,
+        scope_id: ScopeId,
+    ) -> Result<Completion, OwaError> {
+        let raw_calle = value.first().ok_or(OwaError::EmptyCall)?;
+        let raw_calle = self.eval_value(raw_calle, scope_id)?;
+        let callable = raw_calle.as_callable()?;
+
+        callable.eval(self, value.iter().skip(1), scope_id)
+    }
+
+    fn eval_set(
+        &mut self,
+        value: &RedBlackTreeSetSync<OwaAst>,
+        scope_id: ScopeId,
+    ) -> Result<OwaValue, OwaError> {
+        self.eval_collection(value.iter(), scope_id)
+            .map(OwaValue::Set)
+    }
+
+    fn eval_map(
+        &mut self,
+        value: &RedBlackTreeMapSync<OwaAst, OwaAst>,
+        scope_id: ScopeId,
+    ) -> Result<OwaValue, OwaError> {
+        let iter = value.iter().flat_map(|(k, v)| [k, v]);
+        self.eval_collection::<_, Vec<_>>(iter, scope_id)
+            .map(OwaValue::map)
+    }
+
+    /// Evaluates every item in the iterator as a value and collects the results into `B`.
+    ///
+    /// Control-flow signals are forwarded as [`OwaError::Signal`] so they
+    /// propagate virally through argument-evaluation contexts and are later
+    /// caught by the nearest loop / sequence via [`Completion::from_result`].
+    ///
+    /// # Errors
+    ///
+    /// Returns the first [`OwaError`] (including `Signal`) encountered.
+    pub fn eval_collection<'a, C, B>(&mut self, items: C, scope_id: ScopeId) -> Result<B, OwaError>
+    where
+        C: IntoIterator<Item = &'a OwaAst>,
+        B: FromIterator<OwaValue>,
+    {
+        let mut result = Vec::new();
+        for item in items {
+            match self.eval(item, scope_id)? {
+                Completion::Value(v) => result.push(v),
+                Completion::Break => return Err(OwaError::Signal(FlowOperation::Break)),
+                Completion::Continue => return Err(OwaError::Signal(FlowOperation::Continue)),
+                Completion::Return(v) => return Err(OwaError::Signal(FlowOperation::Return(v))),
+            }
+        }
+        Ok(result.into_iter().collect())
+    }
+
+    /// Looks up `name` by walking the scope parent chain without dot-path splitting.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if any scope ID in the chain is invalid.
+    /// Returns [`OwaError::UnboundVariable`] if `name` is not found in any scope.
+    pub fn lookup_expand(&self, scope: ScopeId, name: &str) -> Result<&OwaAst, OwaError> {
+        let scope = self.get_scope(scope)?;
+        if let Some(v) = scope.expand.get(name) {
+            return Ok(v);
+        }
+
+        Err(OwaError::UnboundVariable(name.to_string()))
+    }
+
+    /// Defines a new macro argument `name` in the given scope.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if scope ID is invalid.
+    pub fn set_expand(
+        &mut self,
+        scope: ScopeId,
+        name: &str,
+        value: OwaAst,
+    ) -> Result<(), OwaError> {
+        let scope = self.get_scope_mut(scope)?;
+        scope.expand.insert(name.to_string(), value);
+        Ok(())
+    }
+
+    /// Looks up `name` by walking the scope parent chain without dot-path splitting.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if any scope ID in the chain is invalid.
+    /// Returns [`OwaError::UnboundVariable`] if `name` is not found in any scope.
+    pub fn lookup_runtime_direct(&self, scope: ScopeId, name: &str) -> Result<&OwaValue, OwaError> {
+        let mut scope_id = Some(scope);
+
+        while let Some(s) = scope_id {
+            let scope = self.get_scope(s)?;
+            if let Some(v) = scope.runtime.get(name) {
+                return Ok(v);
+            }
+            scope_id = scope.parent;
+        }
+
+        Err(OwaError::UnboundVariable(name.to_string()))
+    }
+
+    /// Looks up a (potentially dot-separated) `name` in the scope chain.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::UnboundVariable`] if the name (or any path segment) is not found.
+    /// Returns [`OwaError::InvalidMemberAccess`] if a non-map value is accessed as a map.
+    /// Returns [`OwaError::Panic`] if a scope ID is invalid.
+    pub fn lookup_runtime(&self, scope_id: ScopeId, name: &str) -> Result<&OwaValue, OwaError> {
+        // fast path
+        if !name.contains('.') {
+            return self.lookup_runtime_direct(scope_id, name);
+        }
+
+        let mut parts = name.splitn(2, '.');
+        let first_part = parts
+            .next()
+            .ok_or_else(|| OwaError::UnboundVariable(name.to_string()))?;
+        let rest = parts.next();
+
+        let mut current = self.lookup_runtime_direct(scope_id, first_part)?;
+
+        if let Some(rest) = rest {
+            for part in rest.split('.') {
+                let OwaValue::Map(map) = current else {
+                    return Err(OwaError::InvalidMemberAccess(
+                        name.to_string(),
+                        current.type_name(),
+                    ));
+                };
+                let key = OwaValue::kw(part);
+                current = map
+                    .get(&key)
+                    .ok_or_else(|| OwaError::UnboundVariable(name.to_string()))?;
+            }
+        }
+
+        Ok(current)
+    }
+
+    /// Defines a new variable `name` in the given scope.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if `name` is already defined in that scope
+    /// or if the scope ID is invalid.
+    pub fn define_runtime(
+        &mut self,
+        scope: ScopeId,
+        name: &str,
+        value: OwaValue,
+    ) -> Result<(), OwaError> {
+        let scope = self.get_scope_mut(scope)?;
+        if scope.runtime.contains_key(name) {
+            let msg = format!("Variable {name} is already defined in this scope");
+            Err(OwaError::Panic(msg))
+        } else {
+            scope.runtime.insert(name.to_string(), value);
+            Ok(())
+        }
+    }
+
+    /// Updates the value of an existing variable `name`, searching from `scope`
+    /// upward through the parent chain.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::UnboundVariable`] if `name` is not found in any scope.
+    /// Returns [`OwaError::Panic`] if a scope ID is invalid.
+    pub fn set_runtime(
+        &mut self,
+        scope: ScopeId,
+        name: &str,
+        value: OwaValue,
+    ) -> Result<(), OwaError> {
+        let target = self.search_runtime(scope, name)?;
+        let scope_mut = self.get_scope_mut(target)?;
+        if let Some(slot) = scope_mut.runtime.get_mut(name) {
+            *slot = value;
+        } else {
+            scope_mut.runtime.insert(name.to_string(), value);
+        }
+        Ok(())
+    }
+
+    /// Removes the variable `name` from the scope where it is first found.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::UnboundVariable`] if `name` is not found in any scope.
+    /// Returns [`OwaError::Panic`] if a scope ID is invalid.
+    pub fn unset_runtime(&mut self, scope: ScopeId, name: &str) -> Result<(), OwaError> {
+        let target = self.search_runtime(scope, name)?;
+        let scope_mut = self.get_scope_mut(target)?;
+        scope_mut.runtime.remove(name);
+        Ok(())
+    }
+
+    fn search_runtime(&self, scope: ScopeId, name: &str) -> Result<usize, OwaError> {
+        let mut cur = Some(scope);
+        let mut target = None;
+
+        while let Some(s) = cur {
+            let scope_ref = self.get_scope(s)?;
+            if scope_ref.runtime.contains_key(name) {
+                target = Some(s);
+                break;
+            }
+            cur = scope_ref.parent;
+        }
+
+        target.ok_or_else(|| OwaError::UnboundVariable(name.to_string()))
+    }
+
+    pub fn allocate_scope(&mut self, scope: Scope) -> Result<ScopeId, OwaError> {
+        if let Some(free_id) = self.free_list.pop() {
+            self.scopes[free_id] = Some(scope);
+            return Ok(free_id);
+        }
+        if let Some(max) = self.max_scopes_count
+            && self.scopes.len() >= max
+        {
+            return Err(OwaError::Panic("scope limit exceeded".to_string()));
+        }
+        let scope_id = self.scopes.len();
+        self.scopes.push(Some(scope));
+        Ok(scope_id)
+    }
+
+    pub fn inherit_scope(&mut self, parent: ScopeId) -> Result<ScopeId, OwaError> {
+        self.get_scope_mut(parent)?.child_count += 1;
+        self.allocate_scope(Scope::new(Some(parent)))
+    }
+
+    pub fn get_scope_token(&self, scope_id: ScopeId) -> Result<Arc<()>, OwaError> {
+        Ok(self.get_scope(scope_id)?.token.clone())
+    }
+
+    pub fn try_release_scope(&mut self, scope_id: ScopeId) {
+        let Some(scope) = self.scopes.get(scope_id).and_then(|s| s.as_ref()) else {
+            return;
+        };
+        if scope.child_count > 0 {
+            return;
+        }
+        if Arc::strong_count(&scope.token) > 1 {
+            return;
+        }
+        let parent = match scope.parent {
+            Some(p) => p,
+            None => return,
+        };
+        self.scopes[scope_id] = None;
+        self.free_list.push(scope_id);
+
+        if let Some(parent_scope) = self.scopes[parent].as_mut() {
+            parent_scope.child_count = parent_scope.child_count.saturating_sub(1);
+        }
+    }
+
+    /// Returns the parent scope ID of the given scope, if any.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if `scope_id` is invalid.
+    pub fn get_scope_parent(&self, scope_id: ScopeId) -> Result<Option<ScopeId>, OwaError> {
+        let scope = self.get_scope(scope_id)?;
+        Ok(scope.parent)
+    }
+
+    /// Collects all variables visible from `scope_id` (including parent scopes)
+    /// into a map value.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if any scope ID in the chain is invalid.
+    /// Returns [`OwaError::TypeError`] if a parent scope map cannot be read as a map.
+    pub fn get_scope_as_map(&self, scope_id: ScopeId) -> Result<OwaValue, OwaError> {
+        let mut chain = Vec::new();
+        let mut cur = Some(scope_id);
+        while let Some(id) = cur {
+            let scope = self.get_scope(id)?;
+            chain.push(id);
+            cur = scope.parent;
+        }
+
+        let mut map = HashMap::new();
+        for &id in chain.iter().rev() {
+            let scope = self.get_scope(id)?;
+            for (k, v) in &scope.runtime {
+                map.insert(OwaValue::kw(k), v.clone());
+            }
+        }
+
+        map.insert(OwaValue::kw(special_names::IS_SCOPE), OwaValue::int(1));
+
+        Ok(OwaValue::Map(RedBlackTreeMapSync::from_iter(map)))
+    }
+
+    /// Returns a clone of the scope with the given ID.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::Panic`] if `scope_id` does not correspond to a live scope.
+    pub fn get_scope_cloned(&self, scope_id: ScopeId) -> Result<Scope, OwaError> {
+        let scope = self.scopes.get(scope_id).and_then(|inner| inner.as_ref());
+        scope
+            .cloned()
+            .ok_or_else(|| OwaError::Panic(format!("Attempt to access invalid scope {scope_id}")))
+    }
+
+    fn get_scope(&self, scope_id: ScopeId) -> Result<&Scope, OwaError> {
+        let scope = self.scopes.get(scope_id).and_then(|inner| inner.as_ref());
+        scope.ok_or_else(|| OwaError::Panic(format!("Attempt to access invalid scope {scope_id}")))
+    }
+
+    fn get_scope_mut(&mut self, scope_id: ScopeId) -> Result<&mut Scope, OwaError> {
+        let scope = self.scopes.get_mut(scope_id).and_then(|x| x.as_mut());
+        scope.ok_or_else(|| OwaError::Panic(format!("Attempt to access invalid scope {scope_id}")))
+    }
+}
+
+fn resolve_owa_path(base: &std::path::Path) -> Option<String> {
+    [
+        base.to_path_buf(),
+        base.with_extension("owa"),
+        base.join("main.owa"),
+    ]
+    .into_iter()
+    .find(|p| p.is_file())
+    .and_then(|v| v.to_str().map(std::string::ToString::to_string))
+}
+
+fn is_special_symbol(s: &str) -> bool {
+    s.starts_with("__") && s.ends_with("__")
+}
diff --git a/src/core/mod.rs b/src/core/mod.rs
new file mode 100644
index 0000000..f823877
--- /dev/null
+++ b/src/core/mod.rs
@@ -0,0 +1,12 @@
+mod callable;
+mod error;
+mod interpreter;
+mod scope;
+pub mod special_names;
+mod value;
+
+pub use callable::*;
+pub use error::*;
+pub use interpreter::*;
+pub use scope::*;
+pub use value::*;
diff --git a/src/core/scope.rs b/src/core/scope.rs
new file mode 100644
index 0000000..92cdd3a
--- /dev/null
+++ b/src/core/scope.rs
@@ -0,0 +1,77 @@
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use crate::{core::OwaValue, parser::ast::OwaAst};
+
+pub type ScopeId = usize;
+
+#[derive(Debug, Clone)]
+pub struct Scope {
+    pub parent: Option<ScopeId>,
+    pub runtime: HashMap<String, OwaValue>,
+    pub expand: HashMap<String, OwaAst>,
+    pub child_count: usize,
+    pub token: Arc<()>,
+}
+
+impl Default for Scope {
+    fn default() -> Self {
+        Self {
+            parent: None,
+            runtime: HashMap::new(),
+            expand: HashMap::new(),
+            child_count: 0,
+            token: Arc::new(()),
+        }
+    }
+}
+
+impl PartialEq for Scope {
+    fn eq(&self, other: &Self) -> bool {
+        self.parent == other.parent && self.runtime == other.runtime && self.expand == other.expand
+    }
+}
+
+impl Eq for Scope {}
+
+impl Scope {
+    #[must_use]
+    pub fn new(parent: Option<ScopeId>) -> Self {
+        Self {
+            parent,
+            runtime: HashMap::new(),
+            expand: HashMap::new(),
+            child_count: 0,
+            token: Arc::new(()),
+        }
+    }
+
+    #[must_use]
+    pub fn new_with_runtime<K, V, I>(runtime: I) -> Self
+    where
+        K: Into<String>,
+        V: Into<OwaValue>,
+        I: IntoIterator<Item = (K, V)>,
+    {
+        Self {
+            parent: None,
+            runtime: runtime
+                .into_iter()
+                .map(|(k, v)| (k.into(), v.into()))
+                .collect(),
+            expand: HashMap::new(),
+            child_count: 0,
+            token: Arc::new(()),
+        }
+    }
+
+    #[must_use]
+    pub fn local_runtime_to_map(&self) -> OwaValue {
+        OwaValue::Map(
+            self.runtime
+                .iter()
+                .map(|(k, v)| (OwaValue::kw(k), v.clone()))
+                .collect(),
+        )
+    }
+}
diff --git a/src/core/special_names.rs b/src/core/special_names.rs
new file mode 100644
index 0000000..c741902
--- /dev/null
+++ b/src/core/special_names.rs
@@ -0,0 +1,23 @@
+/// Self-reference binding available inside every lambda/macro call body.
+pub const THIS_CALLABLE: &str = "this";
+
+/// Binding containing all arguments passed to the current callable.
+pub const ALL_ARGS: &str = "%%";
+
+/// Binding containing arguments beyond the declared named parameters.
+pub const REST_ARGS: &str = "%&";
+
+/// Runtime variable holding the resolved directory of the currently executing file.
+pub const DIR: &str = "__dir__";
+
+/// Special symbol that evaluates to the current scope as a map value.
+pub const SCOPE: &str = "__scope__";
+
+/// Map key inserted into every scope-map to identify it as a scope object.
+pub const IS_SCOPE: &str = "__is_scope__";
+
+/// Map key that makes a map value callable (callable-object protocol).
+pub const CALL: &str = "__call__";
+
+/// Keyword representing the null / absent value.
+pub const KW_NULL: &str = "null";
diff --git a/src/core/value.rs b/src/core/value.rs
new file mode 100644
index 0000000..d789d71
--- /dev/null
+++ b/src/core/value.rs
@@ -0,0 +1,347 @@
+use num_traits::ToPrimitive;
+use ordered_float::OrderedFloat;
+use rpds::{RedBlackTreeMapSync, RedBlackTreeSetSync, VectorSync};
+use std::{hash::Hash, sync::Arc};
+
+use crate::core::{
+    OwaCallable, OwaCallableCell, OwaError, OwaNativeFunction, OwaNativeMacro, ScopeId,
+    special_names,
+};
+use crate::parser::ast::OwaAst;
+
+/// Formats an iterator of items-with-`unparse()` into a space-separated string.
+#[macro_export]
+macro_rules! vec_unparse {
+    ($iter:expr) => {{
+        $iter
+            .map(|v| v.unparse())
+            .collect::<Vec<String>>()
+            .join(" ")
+    }};
+}
+
+/// Generates constructor and accessor methods shared by `OwaValue` and `OwaAst`.
+///
+/// The `kw()` constructor strips all characters listed in the parser's
+/// `INDENT_IGNORE` set so that keyword identifiers are always clean.
+#[macro_export]
+macro_rules! owa_base_impl {
+    () => {
+        pub fn kw<S: AsRef<str>>(s: S) -> Self {
+            Self::Keyword(Arc::from(s.as_ref()))
+        }
+
+        /// Returns the inner string if this value is a `Keyword`.
+        ///
+        /// # Errors
+        ///
+        /// Returns [`OwaError::TypeError`] if this is not a `Keyword` variant.
+        pub fn as_kw(&self) -> Result<Arc<str>, OwaError> {
+            match self {
+                Self::Keyword(s) => Ok(s.clone()),
+                _ => Err(OwaError::TypeError(
+                    "keyword".into(),
+                    self.type_name().into(),
+                )),
+            }
+        }
+
+        pub fn str<S: AsRef<str>>(s: S) -> Self {
+            Self::Str(Arc::from(s.as_ref()))
+        }
+
+        /// Returns the inner string if this value is a `Str`.
+        ///
+        /// # Errors
+        ///
+        /// Returns [`OwaError::TypeError`] if this is not a `Str` variant.
+        pub fn as_str(&self) -> Result<Arc<str>, OwaError> {
+            match self {
+                Self::Str(s) => Ok(s.clone()),
+                _ => Err(OwaError::TypeError("str".into(), self.type_name().into())),
+            }
+        }
+
+        #[must_use]
+        pub fn to_sym(&self) -> Result<String, OwaError> {
+            match self {
+                Self::Str(s) => Ok(s.as_ref().into()),
+                Self::Keyword(s) => Ok(s.as_ref().into()),
+                _ => Err(OwaError::TypeError(
+                    "str/keyword".into(),
+                    self.type_name().into(),
+                )),
+            }
+        }
+
+        pub fn int<T: ToPrimitive>(i: T) -> Self {
+            Self::Int(i.to_i64().unwrap_or(0))
+        }
+
+        /// Returns the inner integer if this value is an `Int`.
+        ///
+        /// # Errors
+        ///
+        /// Returns [`OwaError::TypeError`] if this is not an `Int` variant.
+        pub fn as_int(&self) -> Result<i64, OwaError> {
+            match self {
+                Self::Int(i) => Ok(*i),
+                _ => Err(OwaError::TypeError("int".into(), self.type_name().into())),
+            }
+        }
+
+        pub const fn float(f: f64) -> Self {
+            Self::Float(OrderedFloat(f))
+        }
+
+        /// Returns the inner float if this value is a `Float`.
+        ///
+        /// # Errors
+        ///
+        /// Returns [`OwaError::TypeError`] if this is not a `Float` variant.
+        pub fn as_float(&self) -> Result<OrderedFloat<f64>, OwaError> {
+            match self {
+                Self::Float(f) => Ok(*f),
+                _ => Err(OwaError::TypeError("float".into(), self.type_name().into())),
+            }
+        }
+
+        pub fn map<C>(coll: C) -> Self
+        where
+            C: IntoIterator<Item = Self>,
+        {
+            let mut map = RedBlackTreeMapSync::default();
+            let mut iter = coll.into_iter();
+
+            while let (Some(k), Some(v)) = (iter.next(), iter.next()) {
+                map = map.insert(k, v);
+            }
+
+            Self::Map(map)
+        }
+
+        /// Returns a reference to the inner map if this value is a `Map`.
+        ///
+        /// # Errors
+        ///
+        /// Returns [`OwaError::TypeError`] if this is not a `Map` variant.
+        pub fn as_map(&self) -> Result<&RedBlackTreeMapSync<Self, Self>, OwaError> {
+            match self {
+                Self::Map(m) => Ok(m),
+                _ => Err(OwaError::TypeError("map".into(), self.type_name().into())),
+            }
+        }
+
+        #[must_use]
+        pub fn vec<C>(coll: C) -> Self
+        where
+            C: IntoIterator<Item = Self>,
+        {
+            Self::Vec(VectorSync::from_iter(coll.into_iter()))
+        }
+
+        #[must_use]
+        pub fn to_vec(self) -> Self {
+            Self::Vec(VectorSync::from_iter(vec![self]))
+        }
+
+        /// Returns a reference to the inner vector if this value is a `Vec`.
+        ///
+        /// # Errors
+        ///
+        /// Returns [`OwaError::TypeError`] if this is not a `Vec` variant.
+        pub fn as_vec(&self) -> Result<&VectorSync<Self>, OwaError> {
+            match self {
+                Self::Vec(v) => Ok(v),
+                _ => Err(OwaError::TypeError("vec".into(), self.type_name().into())),
+            }
+        }
+
+        /// Returns a reference to the inner set if this value is a `Set`.
+        ///
+        /// # Errors
+        ///
+        /// Returns [`OwaError::TypeError`] if this is not a `Set` variant.
+        pub fn as_set(&self) -> Result<&RedBlackTreeSetSync<Self>, OwaError> {
+            match self {
+                Self::Set(s) => Ok(s),
+                _ => Err(OwaError::TypeError("set".into(), self.type_name().into())),
+            }
+        }
+
+        #[must_use]
+        pub fn set<C>(coll: C) -> Self
+        where
+            C: IntoIterator<Item = Self>,
+        {
+            Self::Set(RedBlackTreeSetSync::from_iter(coll.into_iter()))
+        }
+
+        #[must_use]
+        pub fn to_set(self) -> Self {
+            Self::Set(RedBlackTreeSetSync::from_iter(vec![self]))
+        }
+    };
+}
+
+#[derive(Hash, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[non_exhaustive]
+pub enum OwaValue {
+    Keyword(Arc<str>),                    // :ident
+    Str(Arc<str>),                        // "..."
+    Float(OrderedFloat<f64>),             // 1.0
+    Int(i64),                             // 1
+    Vec(VectorSync<Self>),                // [...]
+    Set(RedBlackTreeSetSync<Self>),       // {...}
+    Map(RedBlackTreeMapSync<Self, Self>), // #{...}
+    Quote(Arc<OwaAst>),                   // '...
+    Callable(OwaCallable),
+}
+
+impl OwaValue {
+    owa_base_impl!();
+
+    #[must_use]
+    pub fn new_macro(
+        body: OwaAst,
+        params: VectorSync<Arc<str>>,
+        scope_id: ScopeId,
+        scope_token: Arc<()>,
+    ) -> Self {
+        Self::Callable(OwaCallable {
+            scope_id,
+            scope_token,
+            params,
+            body: OwaCallableCell::Macro(Arc::new(body)),
+        })
+    }
+
+    #[must_use]
+    pub fn new_lambda(
+        body: OwaAst,
+        params: VectorSync<Arc<str>>,
+        scope_id: ScopeId,
+        scope_token: Arc<()>,
+    ) -> Self {
+        Self::Callable(OwaCallable {
+            scope_id,
+            scope_token,
+            params,
+            body: OwaCallableCell::Lambda(Arc::new(body)),
+        })
+    }
+
+    /// Returns the callable wrapped by this value, following `__call__` map keys.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::TypeError`] if the value (or the resolved `__call__`
+    /// chain) is not a `Callable` variant.
+    pub fn as_callable(&self) -> Result<&OwaCallable, OwaError> {
+        let mut calle = self;
+
+        // magic __call__
+        while let Self::Map(items) = calle {
+            let item = items.get(&Self::kw(special_names::CALL));
+            match item {
+                Some(v) => calle = v,
+                None => break,
+            }
+        }
+
+        match calle {
+            Self::Callable(lambda) => Ok(lambda),
+            _ => Err(OwaError::TypeError(
+                "lambda or macro".into(),
+                calle.type_name().into(),
+            )),
+        }
+    }
+
+    pub fn native_function(function: OwaNativeFunction) -> Self {
+        Self::native(OwaCallableCell::NativeLambda(function))
+    }
+
+    pub fn native_macro(r#macro: OwaNativeMacro) -> Self {
+        Self::native(OwaCallableCell::NativeMacro(r#macro))
+    }
+
+    fn native(body: OwaCallableCell) -> Self {
+        Self::Callable(OwaCallable {
+            scope_id: 0,
+            scope_token: Arc::new(()),
+            params: VectorSync::from_iter(vec![]),
+            body,
+        })
+    }
+
+    #[must_use]
+    pub const fn quote(value: Arc<OwaAst>) -> Self {
+        Self::Quote(value)
+    }
+
+    /// Returns the inner AST node if this value is a `Quote`.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::TypeError`] if this is not a `Quote` variant.
+    pub fn as_quote(&self) -> Result<Arc<OwaAst>, OwaError> {
+        match self {
+            Self::Quote(q) => Ok(q.clone()),
+            _ => Err(OwaError::TypeError("quote".into(), self.type_name().into())),
+        }
+    }
+
+    #[must_use]
+    #[allow(clippy::missing_const_for_fn)]
+    pub fn type_name(&self) -> &'static str {
+        match self {
+            Self::Keyword(_) => "keyword",
+            Self::Str(_) => "str",
+            Self::Float(_) => "float",
+            Self::Int(_) => "int",
+            Self::Vec(_) => "vec",
+            Self::Set(_) => "set",
+            Self::Map(_) => "map",
+            Self::Quote(_) => "quote",
+            Self::Callable(lambda) => lambda.type_name(),
+        }
+    }
+
+    #[must_use]
+    pub fn unparse(&self) -> String {
+        match self {
+            Self::Keyword(s) => format!(":{s}"),
+            Self::Str(s) => format!("\"{s}\""),
+            Self::Float(f) => {
+                let s = format!("{f}");
+                if s.contains('.') { s } else { format!("{s}.0") }
+            }
+            Self::Int(i) => i.to_string(),
+            Self::Vec(v) => {
+                format!("[{}]", vec_unparse!(v.iter()))
+            }
+            Self::Set(v) => {
+                format!("#{{{}}}", vec_unparse!(v.iter()))
+            }
+            Self::Map(v) => format!(
+                "{{{}}}",
+                vec_unparse!(v.iter().flat_map(|(k, v)| vec![k, v]))
+            ),
+            Self::Quote(v) => format!("'{}", v.unparse()),
+            Self::Callable(v) => v.unparse(),
+        }
+    }
+}
+
+impl std::fmt::Debug for OwaValue {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.unparse())
+    }
+}
+
+impl From<&str> for OwaValue {
+    fn from(val: &str) -> Self {
+        Self::Str(Arc::from(val))
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..c449de0
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,18 @@
+#![warn(
+    clippy::all,
+    clippy::pedantic,
+    clippy::nursery,
+    clippy::cargo,
+    clippy::perf
+)]
+#![allow(
+    clippy::multiple_crate_versions, // idk how to fix this
+    clippy::cast_possible_truncation,
+    clippy::cast_sign_loss,
+    clippy::needless_continue
+)]
+#![cfg_attr(test, allow(clippy::needless_pass_by_value))]
+
+pub mod builtins;
+pub mod core;
+pub mod parser;
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..58edcf7
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,51 @@
+use owa_rs::{
+    builtins,
+    core::{Interpreter, OwaValue, Scope, special_names},
+};
+use tracing::error;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tracing_subscriber::fmt::init();
+
+    // flags
+    let argv = std::env::args().collect::<Vec<String>>();
+    let argv = argv.iter().map(|s| s.as_str()).collect::<Vec<_>>();
+    let no_owu = argv.contains(&"--no-owu");
+
+    // builtins
+    let builtins = [("builtins", builtins::scope().local_runtime_to_map())];
+
+    // init root scope
+    let mut interpreter = Interpreter::new(None);
+    let scope = Scope::new_with_runtime(builtins);
+    let scope_id = interpreter.allocate_scope(scope).unwrap();
+    let cwd = std::env::current_dir().unwrap_or_else(|_| std::path::PathBuf::from("."));
+    interpreter
+        .define_runtime(
+            scope_id,
+            special_names::DIR,
+            OwaValue::str(cwd.to_str().unwrap_or(".")),
+        )
+        .unwrap();
+
+    // eval target
+    let target_path = if no_owu {
+        let target = argv.iter().find(|s| s.ends_with(".owa"));
+        if let Some(target) = target {
+            target
+        } else {
+            error!("No owa file specified");
+            std::process::exit(1);
+        }
+    } else {
+        "modules/owu/main.owa"
+    };
+    interpreter
+        .run(target_path, scope_id)
+        .unwrap_or_else(|err| {
+            error!("Failed to load owu: {}", err.message());
+            std::process::exit(1)
+        });
+
+    Ok(())
+}
diff --git a/src/parser/annotation.rs b/src/parser/annotation.rs
new file mode 100644
index 0000000..6fe4b17
--- /dev/null
+++ b/src/parser/annotation.rs
@@ -0,0 +1,37 @@
+use nom::{
+    IResult, Parser as _, bytes::complete::tag, character::multispace0, combinator::cut,
+    sequence::delimited,
+};
+
+use crate::parser::{OwaAst, parse_value, ws};
+
+pub(super) fn parse_annotation(input: &str) -> IResult<&str, OwaAst> {
+    delimited(
+        ws(tag("<")),
+        cut(parse_value),
+        cut((multispace0(), tag(">"))),
+    )
+    .parse(input)
+}
+
+#[test]
+fn test_annotation() {
+    assert_eq!(
+        parse_annotation("<(:a :b :c)>"),
+        Ok((
+            "",
+            OwaAst::call([OwaAst::kw("a"), OwaAst::kw("b"), OwaAst::kw("c")])
+        ))
+    );
+    assert_eq!(
+        parse_annotation("<(:a [:b :c] [(:d)])>garbage"),
+        Ok((
+            "garbage",
+            OwaAst::call([
+                OwaAst::kw("a"),
+                OwaAst::vec([OwaAst::kw("b"), OwaAst::kw("c"),]),
+                OwaAst::vec([OwaAst::call([OwaAst::kw("d")]),]),
+            ])
+        ))
+    );
+}
diff --git a/src/parser/ast.rs b/src/parser/ast.rs
new file mode 100644
index 0000000..d07a98b
--- /dev/null
+++ b/src/parser/ast.rs
@@ -0,0 +1,353 @@
+use super::to_indent;
+use crate::{
+    core::{Interpreter, OwaError, OwaValue, special_names},
+    owa_base_impl, vec_unparse,
+};
+use num_traits::ToPrimitive;
+use ordered_float::OrderedFloat;
+use rpds::{RedBlackTreeMapSync, RedBlackTreeSetSync, VectorSync};
+use std::sync::Arc;
+
+#[derive(Debug, Hash, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[warn(unpredictable_function_pointer_comparisons)]
+pub struct OwaAnnotation {
+    pub annotation: Arc<OwaAst>,
+    pub value: Arc<OwaAst>,
+}
+
+#[derive(Hash, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[warn(unpredictable_function_pointer_comparisons)]
+#[non_exhaustive]
+pub enum OwaAst {
+    Annotation(OwaAnnotation),            // <...>...
+    Call(VectorSync<Self>),               // (...)
+    Float(OrderedFloat<f64>),             // 1.0
+    Int(i64),                             // 1
+    Keyword(Arc<str>),                    // :ident
+    Lambda(VectorSync<Self>),             // #(...)
+    Map(RedBlackTreeMapSync<Self, Self>), // #{...}
+    Quote(Arc<Self>),                     // '...
+    Set(RedBlackTreeSetSync<Self>),       // {...}
+    Str(Arc<str>),                        // "..."
+    Symbol(Arc<str>),                     // ident
+    Unquote(Arc<Self>),                   // $...
+    Vec(VectorSync<Self>),                // [...]
+}
+
+impl OwaAst {
+    owa_base_impl!();
+
+    #[must_use]
+    pub fn call<C>(coll: C) -> Self
+    where
+        C: IntoIterator<Item = Self>,
+    {
+        Self::Call(VectorSync::from_iter(coll))
+    }
+
+    #[must_use]
+    pub fn to_call(self) -> Self {
+        Self::Call(VectorSync::from_iter([self]))
+    }
+
+    /// Returns a reference to the inner vector if this node is a [`OwaAst::Call`].
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::TypeError`] if this node is not the `Call` variant.
+    pub fn as_call(&self) -> Result<&VectorSync<Self>, OwaError> {
+        match self {
+            Self::Call(v) => Ok(v),
+            _ => Err(OwaError::TypeError("call".into(), self.type_name().into())),
+        }
+    }
+
+    pub fn new_lambda<B>(body: B) -> Self
+    where
+        B: IntoIterator<Item = Self>,
+    {
+        Self::Lambda(VectorSync::from_iter(body))
+    }
+
+    pub fn sym<S: AsRef<str>>(s: S) -> Self {
+        let s = to_indent(s);
+        Self::Symbol(Arc::from(s))
+    }
+
+    /// Returns the inner symbol string if this node is a [`OwaAst::Symbol`].
+    ///
+    /// # Errors
+    ///
+    /// Returns [`OwaError::TypeError`] if this node is not the `Symbol` variant.
+    pub fn as_sym(&self) -> Result<Arc<str>, OwaError> {
+        match self {
+            Self::Symbol(s) => Ok(s.clone()),
+            _ => Err(OwaError::TypeError(
+                "symbol".into(),
+                self.type_name().into(),
+            )),
+        }
+    }
+
+    #[must_use]
+    pub fn new_quote(v: Self) -> Self {
+        Self::Quote(Arc::from(v))
+    }
+
+    #[must_use]
+    pub fn to_quote(self) -> Self {
+        Self::Quote(Arc::from(self))
+    }
+
+    #[must_use]
+    pub fn new_unquote(v: Self) -> Self {
+        Self::Unquote(Arc::from(v))
+    }
+
+    #[must_use]
+    pub fn to_unquote(self) -> Self {
+        Self::Unquote(Arc::from(self))
+    }
+
+    #[must_use]
+    pub fn to_annotation(self, ann: Self) -> Self {
+        Self::Annotation(OwaAnnotation {
+            annotation: Arc::from(ann),
+            value: Arc::from(self),
+        })
+    }
+
+    #[must_use]
+    pub fn type_name(&self) -> &'static str {
+        match self {
+            Self::Symbol(_) => "symbol",
+            Self::Keyword(_) => "keyword",
+            Self::Str(_) => "str",
+            Self::Float(_) => "float",
+            Self::Int(_) => "int",
+            Self::Vec(_) => "vec",
+            Self::Call(_) => "call",
+            Self::Set(_) => "set",
+            Self::Map(_) => "map",
+            Self::Quote(_) => "quote",
+            Self::Unquote(_) => "unquote",
+            Self::Lambda(_) => "lambda",
+            Self::Annotation(v) => v.value.type_name(),
+        }
+    }
+
+    #[must_use]
+    pub fn unparse(&self) -> String {
+        match self {
+            Self::Symbol(v) => v.to_string(),
+            Self::Keyword(v) => format!(":{v}"),
+            Self::Str(v) => format!("\"{v}\""),
+            Self::Float(v) => {
+                let s = format!("{v}");
+                if s.contains('.') { s } else { format!("{s}.0") }
+            }
+            Self::Int(v) => v.to_string(),
+            Self::Vec(v) => {
+                format!("[{}]", vec_unparse!(v.iter()))
+            }
+            Self::Call(v) => format!("({})", vec_unparse!(v.iter())),
+            Self::Set(v) => {
+                format!("#{{{}}}", vec_unparse!(v.iter()))
+            }
+            Self::Map(v) => format!("{{{}}}", vec_unparse!(v.iter().flat_map(|(k, v)| [k, v]))),
+            Self::Quote(v) => format!("'{}", v.unparse()),
+            Self::Unquote(v) => format!("${}", v.unparse()),
+            Self::Lambda(v) => format!("#({})", vec_unparse!(v.iter())),
+            Self::Annotation(ann) => {
+                format!("<{}>{}", ann.annotation.unparse(), ann.value.unparse())
+            }
+        }
+    }
+
+    #[must_use]
+    pub fn to_str(&self) -> String {
+        match self {
+            Self::Symbol(s) => s.to_string(),
+            Self::Str(s) => s.as_ref().to_string(),
+            _ => self.unparse(),
+        }
+    }
+
+    #[must_use]
+    pub fn unannotate(&self) -> Self {
+        match self {
+            Self::Annotation(ann) => ann.value.unannotate(),
+            Self::Vec(v) => Self::Vec(v.iter().map(Self::unannotate).collect()),
+            Self::Call(v) => Self::Call(v.iter().map(Self::unannotate).collect()),
+            Self::Set(v) => Self::Set(v.iter().map(Self::unannotate).collect()),
+            Self::Map(v) => Self::map(
+                v.iter()
+                    .flat_map(|(k, v)| [Self::unannotate(k), Self::unannotate(v)]),
+            ),
+            Self::Lambda(v) => Self::Lambda(v.iter().map(Self::unannotate).collect()),
+            Self::Quote(v) => Self::Quote(Arc::from(v.unannotate())),
+            Self::Unquote(v) => Self::Unquote(Arc::from(v.unannotate())),
+            _ => self.clone(),
+        }
+    }
+
+    #[must_use]
+    pub fn pack(&self) -> OwaValue {
+        let type_name = OwaValue::kw(self.type_name());
+        let data = match self {
+            Self::Symbol(v) => OwaValue::str(v),
+            Self::Keyword(v) => OwaValue::kw(v),
+            Self::Str(v) => OwaValue::str(v),
+            Self::Float(v) => OwaValue::float(v.into_inner()),
+            Self::Int(v) => OwaValue::Int(*v),
+            Self::Vec(v) => OwaValue::vec(v.iter().map(Self::pack)),
+            Self::Call(v) => OwaValue::vec(v.iter().map(Self::pack)),
+            Self::Set(v) => OwaValue::set(v.iter().map(Self::pack)),
+            Self::Map(v) => OwaValue::map(v.iter().flat_map(|(k, v)| [k.pack(), v.pack()])),
+            Self::Quote(v) => OwaValue::quote(v.clone()),
+            Self::Unquote(v) => v.pack(),
+            Self::Lambda(v) => OwaValue::vec(v.iter().map(Self::pack)),
+            Self::Annotation(v) => OwaValue::map(vec![
+                OwaValue::kw("value"),
+                v.value.as_ref().pack(),
+                OwaValue::kw("annotation"),
+                v.annotation.as_ref().pack(),
+            ]),
+        };
+        OwaValue::map(vec![
+            OwaValue::kw("type"),
+            type_name,
+            OwaValue::kw("data"),
+            data,
+        ])
+    }
+}
+
+pub struct Expander<'a> {
+    interpreter: &'a mut Interpreter,
+    scope_id: usize,
+}
+
+impl<'a> Expander<'a> {
+    pub const fn new(interpreter: &'a mut Interpreter, scope_id: usize) -> Self {
+        Self {
+            interpreter,
+            scope_id,
+        }
+    }
+
+    #[must_use]
+    pub fn expand(&self, ast: &OwaAst, in_unquote: bool, in_quote: bool) -> OwaAst {
+        self.expand_priv(ast, in_unquote, in_quote)
+            .pop()
+            .unwrap_or_else(|| ast.clone())
+    }
+
+    #[must_use]
+    fn resolve(&self, sym: &str) -> Vec<OwaAst> {
+        let result = match sym {
+            special_names::ALL_ARGS | special_names::REST_ARGS => {
+                let val = self.interpreter.lookup_expand(self.scope_id, sym);
+                val.and_then(|v| v.as_vec())
+                    .map(|v| v.iter().cloned().collect::<Vec<_>>())
+            }
+            _ => {
+                let val = self.interpreter.lookup_expand(self.scope_id, sym);
+                val.map(|v| vec![v.clone()])
+            }
+        };
+        result.unwrap_or_else(|_| vec![OwaAst::sym(sym)])
+    }
+
+    #[must_use]
+    fn expand_priv(&self, ast: &OwaAst, in_unquote: bool, in_quote: bool) -> Vec<OwaAst> {
+        match ast {
+            OwaAst::Symbol(s) => {
+                if !in_unquote {
+                    return vec![ast.clone()];
+                }
+                self.resolve(s.as_ref())
+            }
+            OwaAst::Vec(v) => {
+                let transformed = v.iter().map(|v| self.expand_priv(v, in_unquote, in_quote));
+                vec![OwaAst::vec(transformed.flatten())]
+            }
+            OwaAst::Call(v) => {
+                let transformed = v.iter().map(|v| self.expand_priv(v, in_unquote, in_quote));
+                vec![OwaAst::call(transformed.flatten())]
+            }
+            OwaAst::Set(v) => {
+                let transformed = v.iter().map(|v| self.expand_priv(v, in_unquote, in_quote));
+                vec![OwaAst::set(transformed.flatten())]
+            }
+            OwaAst::Map(v) => {
+                let transformed = v.iter().flat_map(|(k, v)| {
+                    [
+                        self.expand_priv(k, in_unquote, in_quote),
+                        self.expand_priv(v, in_unquote, in_quote),
+                    ]
+                });
+                vec![OwaAst::map(transformed.flatten())]
+            }
+            OwaAst::Lambda(v) => {
+                let transformed = v.iter().map(|v| self.expand_priv(v, in_unquote, in_quote));
+                vec![OwaAst::new_lambda(transformed.flatten())]
+            }
+            OwaAst::Quote(v) => vec![if in_quote {
+                ast.clone()
+            } else {
+                v.as_ref().clone()
+            }],
+            OwaAst::Unquote(v) => {
+                if in_unquote {
+                    vec![ast.clone()]
+                } else {
+                    self.expand_priv(v, true, in_quote)
+                }
+            }
+            _ => vec![ast.clone()],
+        }
+    }
+}
+
+impl std::fmt::Debug for OwaAst {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.unparse())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_case::test_case;
+
+    #[test_case(OwaAst::sym("foo"), "foo")]
+    #[test_case(OwaAst::kw("foo"), ":foo")]
+    #[test_case(OwaAst::str("foo"), "\"foo\"")]
+    #[test_case(OwaAst::float(1.0), "1.0")]
+    #[test_case(OwaAst::float(1.2), "1.2")]
+    #[test_case(OwaAst::float(1.234), "1.234")]
+    #[test_case(
+        OwaAst::vec([OwaAst::int(1), OwaAst::str("foo"), OwaAst::kw("a")]),
+        "[1 \"foo\" :a]"
+    )]
+    #[test_case(
+        OwaAst::call([OwaAst::int(1), OwaAst::float(1.0), OwaAst::kw("b"), OwaAst::str("foo")]),
+        "(1 1.0 :b \"foo\")"
+    )]
+    #[test_case(
+        OwaAst::set([OwaAst::int(1), OwaAst::float(1.0), OwaAst::kw("b"), OwaAst::str("foo")]),
+        "#{1.0 1 :b \"foo\"}"
+    )]
+    #[test_case(
+        OwaAst::map([
+            OwaAst::int(1), OwaAst::float(1.0),
+            OwaAst::kw("b"), OwaAst::str("foo"),
+            OwaAst::str("foo"), OwaAst::kw("b")
+        ]),
+        "{1 1.0 :b \"foo\" \"foo\" :b}"
+    )]
+    fn unparse_tests(value: OwaAst, expected: &str) {
+        assert_eq!(value.unparse(), expected);
+    }
+}
diff --git a/src/parser/call.rs b/src/parser/call.rs
new file mode 100644
index 0000000..7e806f8
--- /dev/null
+++ b/src/parser/call.rs
@@ -0,0 +1,29 @@
+use nom::{IResult, Parser as _, combinator::map};
+
+use crate::parser::{OwaAst, collection};
+
+pub(super) fn parse_call(input: &str) -> IResult<&str, OwaAst> {
+    map(collection("(", ")"), OwaAst::call).parse(input)
+}
+
+#[test]
+fn test_call() {
+    assert_eq!(
+        parse_call("(:a :b :c)"),
+        Ok((
+            "",
+            OwaAst::call([OwaAst::kw("a"), OwaAst::kw("b"), OwaAst::kw("c")])
+        ))
+    );
+    assert_eq!(
+        parse_call("(:a [:b :c] [(:d)])garbage"),
+        Ok((
+            "garbage",
+            OwaAst::call([
+                OwaAst::kw("a"),
+                OwaAst::vec([OwaAst::kw("b"), OwaAst::kw("c"),]),
+                OwaAst::vec([OwaAst::call([OwaAst::kw("d")]),]),
+            ])
+        ))
+    );
+}
diff --git a/src/parser/keyword.rs b/src/parser/keyword.rs
new file mode 100644
index 0000000..d3d707e
--- /dev/null
+++ b/src/parser/keyword.rs
@@ -0,0 +1,14 @@
+use nom::{IResult, Parser as _, bytes::complete::tag, combinator::map, sequence::preceded};
+
+use crate::parser::{OwaAst, identifier};
+
+pub(super) fn parse_keyword(input: &str) -> IResult<&str, OwaAst> {
+    map(preceded(tag(":"), identifier), OwaAst::kw).parse(input)
+}
+
+#[test]
+fn test_keyword() {
+    assert_eq!(parse_keyword(":foo"), Ok(("", OwaAst::kw("foo"))));
+    assert_eq!(parse_keyword(":foo1232"), Ok(("", OwaAst::kw("foo1232"))));
+    assert_eq!(parse_keyword(":foo:s"), Ok((":s", OwaAst::kw("foo"))));
+}
diff --git a/src/parser/lambda.rs b/src/parser/lambda.rs
new file mode 100644
index 0000000..b179763
--- /dev/null
+++ b/src/parser/lambda.rs
@@ -0,0 +1,30 @@
+use nom::{IResult, Parser as _, combinator::map};
+
+use crate::parser::{OwaAst, collection};
+
+pub(super) fn parse_lambda(input: &str) -> IResult<&str, OwaAst> {
+    map(collection("#(", ")"), OwaAst::new_lambda).parse(input)
+}
+
+#[test]
+fn test_call() {
+    assert_eq!(
+        parse_lambda("#(:a :b :c)"),
+        Ok((
+            "",
+            OwaAst::new_lambda([OwaAst::kw("a"), OwaAst::kw("b"), OwaAst::kw("c")])
+        ))
+    );
+    assert_eq!(
+        parse_lambda("#(:a [:b :c] [(:d)] #(:e))garbage"),
+        Ok((
+            "garbage",
+            OwaAst::new_lambda([
+                OwaAst::kw("a"),
+                OwaAst::vec([OwaAst::kw("b"), OwaAst::kw("c")]),
+                OwaAst::vec([OwaAst::call([OwaAst::kw("d")])]),
+                OwaAst::new_lambda([OwaAst::kw("e")])
+            ])
+        ))
+    );
+}
diff --git a/src/parser/map.rs b/src/parser/map.rs
new file mode 100644
index 0000000..c086960
--- /dev/null
+++ b/src/parser/map.rs
@@ -0,0 +1,39 @@
+use nom::{IResult, Parser as _, combinator::map};
+
+use crate::parser::{OwaAst, collection};
+
+pub(super) fn parse_map(input: &str) -> IResult<&str, OwaAst> {
+    map(collection("{", "}"), OwaAst::map).parse(input)
+}
+
+#[test]
+fn test_call() {
+    assert_eq!(
+        parse_map("{:a :b :c}"),
+        Ok(("", OwaAst::map([OwaAst::kw("a"), OwaAst::kw("b")])))
+    );
+    assert_eq!(
+        parse_map("{:a :b :c :d}"),
+        Ok((
+            "",
+            OwaAst::map([
+                OwaAst::kw("a"),
+                OwaAst::kw("b"),
+                OwaAst::kw("c"),
+                OwaAst::kw("d")
+            ])
+        ))
+    );
+    assert_eq!(
+        parse_map("{:a #{:b :c} [(:d)] :e}garbage"),
+        Ok((
+            "garbage",
+            OwaAst::map([
+                OwaAst::kw("a"),
+                OwaAst::set([OwaAst::kw("b"), OwaAst::kw("c")]),
+                OwaAst::vec([OwaAst::call([OwaAst::kw("d"),]),]),
+                OwaAst::kw("e")
+            ])
+        ))
+    );
+}
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
new file mode 100644
index 0000000..ea5f9e7
--- /dev/null
+++ b/src/parser/mod.rs
@@ -0,0 +1,163 @@
+use nom::{
+    IResult, Parser,
+    branch::alt,
+    bytes::complete::{is_not, tag},
+    character::complete::multispace1,
+    combinator::{cut, map, recognize},
+    error::Error,
+    multi::{many0, many1},
+    sequence::{delimited, pair, preceded},
+};
+
+mod annotation;
+pub mod ast;
+mod call;
+mod keyword;
+mod lambda;
+mod map;
+mod number;
+mod quote;
+mod set;
+mod string;
+mod symbol;
+mod unquote;
+mod vector;
+
+use annotation::parse_annotation;
+use ast::OwaAst;
+use call::parse_call;
+use keyword::parse_keyword;
+use map::parse_map;
+use number::{parse_float, parse_integer};
+use quote::parse_quote;
+use set::parse_set;
+use string::parse_string;
+use symbol::parse_symbol;
+use unquote::parse_unquote;
+use vector::parse_vector;
+
+use crate::parser::lambda::parse_lambda;
+
+pub(crate) const INDENT_IGNORE: &str = " \t\n\r,;:{}[]()<>$#\"'";
+
+pub(crate) fn to_indent<S: AsRef<str>>(s: S) -> String {
+    s.as_ref()
+        .chars()
+        .filter(|c| !INDENT_IGNORE.contains(*c))
+        .collect()
+}
+
+fn identifier(input: &str) -> IResult<&str, &str> {
+    recognize(many1(is_not(INDENT_IGNORE))).parse(input)
+}
+
+fn parse_comment(input: &str) -> IResult<&str, ()> {
+    map(preceded(tag(";;"), is_not("\n")), |_| ()).parse(input)
+}
+
+fn skip_ws(input: &str) -> IResult<&str, ()> {
+    map(
+        many0(alt((map(multispace1, |_| ()), parse_comment))),
+        |_| (),
+    )
+    .parse(input)
+}
+
+fn collection<'a>(
+    start: &str,
+    end: &str,
+) -> impl Parser<&'a str, Output = Vec<OwaAst>, Error = Error<&'a str>> {
+    delimited(
+        ws(tag(start)),
+        cut(many0(parse_value)),
+        cut((skip_ws, tag(end))),
+    )
+}
+
+fn ws<'a, O, F>(inner: F) -> impl Parser<&'a str, Output = O, Error = Error<&'a str>>
+where
+    F: Parser<&'a str, Output = O, Error = Error<&'a str>>,
+{
+    delimited(skip_ws, inner, skip_ws)
+}
+
+fn parse_atom(input: &str) -> IResult<&str, OwaAst> {
+    preceded(
+        skip_ws,
+        alt((
+            parse_float, // must be before parse_integer
+            parse_integer,
+            parse_string,
+            parse_keyword, // must be before parse_symbol
+            parse_symbol,
+            parse_lambda, // must be before parse_call
+            parse_call,
+            parse_set, // must be before parse_map
+            parse_map,
+            parse_vector,
+            parse_unquote,
+            parse_quote,
+        )),
+    )
+    .parse(input)
+}
+
+/// Parses a single OWA value (with optional leading annotations) from `input`.
+///
+/// # Errors
+///
+/// Returns a [`nom::Err`] if the input does not contain a valid OWA expression.
+pub fn parse_value(input: &str) -> IResult<&str, OwaAst> {
+    map(
+        pair(many0(parse_annotation), parse_atom),
+        |(annotations, value)| {
+            let mut result = value;
+            for annotation in annotations {
+                result = result.to_annotation(annotation);
+            }
+            result
+        },
+    )
+    .parse(input)
+}
+
+/// Reads a file from disk and parses its contents as a single OWA value.
+///
+/// # Errors
+///
+/// Returns an error string if the file cannot be read or if its contents
+/// cannot be parsed as a valid OWA expression.
+pub fn parse_file(raw_filename: &str) -> Result<OwaAst, String> {
+    let content = std::fs::read_to_string(raw_filename)
+        .map_err(|err| format!("Failed to read file {raw_filename}: {err}"))?;
+
+    match parse_value(&content) {
+        Ok((_, value)) => Ok(value),
+        Err(err) => Err(format!("Failed to parse file {raw_filename}: {err:?}")),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use test_case::test_case;
+
+    #[test_case("(1 2 3)", OwaAst::call([OwaAst::int(1), OwaAst::int(2), OwaAst::int(3)]))]
+    #[test_case(r#"("hi" 1 "bye")"#, OwaAst::call([OwaAst::str("hi"), OwaAst::int(1), OwaAst::str("bye")]))]
+    #[test_case("[1 2 3]", OwaAst::vec([OwaAst::int(1), OwaAst::int(2), OwaAst::int(3)]))]
+    #[test_case(r#"["hello world!" 1 "bye"]"#, OwaAst::vec([OwaAst::str("hello world!"), OwaAst::int(1), OwaAst::str("bye")]))]
+    #[test_case(";; comment\n(1 2 3)", OwaAst::call([OwaAst::int(1), OwaAst::int(2), OwaAst::int(3)]))]
+    #[test_case("(1 ;; comment\n 2 3)", OwaAst::call([OwaAst::int(1), OwaAst::int(2), OwaAst::int(3)]))]
+    #[test_case("(1 2 ;; comment\n 3)", OwaAst::call([OwaAst::int(1), OwaAst::int(2), OwaAst::int(3)]))]
+    #[test_case("(1 2 3) ;; trailing comment", OwaAst::call([OwaAst::int(1), OwaAst::int(2), OwaAst::int(3)]))]
+    fn parse_tests(input: &str, expected: OwaAst) {
+        assert_eq!(parse_value(input).unwrap().1, expected);
+    }
+
+    #[test]
+    fn parse_comment_test() {
+        let input = ";; this is a comment\n(1 2 3)";
+        let expected = OwaAst::call([OwaAst::int(1), OwaAst::int(2), OwaAst::int(3)]);
+        assert_eq!(parse_value(input).unwrap().1, expected);
+    }
+}
diff --git a/src/parser/number.rs b/src/parser/number.rs
new file mode 100644
index 0000000..4fcfad4
--- /dev/null
+++ b/src/parser/number.rs
@@ -0,0 +1,170 @@
+use nom::{
+    IResult, Parser as _,
+    branch::alt,
+    bytes::complete::tag,
+    character::complete::{char, one_of},
+    combinator::{map_res, opt, recognize},
+    multi::{many0, many1},
+    sequence::{preceded, terminated},
+};
+
+use crate::parser::OwaAst;
+
+fn hexadecimal(input: &str) -> IResult<&str, isize> {
+    map_res(
+        preceded(
+            alt((tag("0x"), tag("0X"))),
+            recognize(many1(terminated(
+                one_of("0123456789abcdefABCDEF"),
+                many0(char('_')),
+            ))),
+        ),
+        |out: &str| isize::from_str_radix(&str::replace(out, "_", ""), 16),
+    )
+    .parse(input)
+}
+
+fn octal(input: &str) -> IResult<&str, isize> {
+    map_res(
+        preceded(
+            alt((tag("0o"), tag("0O"))),
+            recognize(many1(terminated(one_of("01234567"), many0(char('_'))))),
+        ),
+        |out: &str| isize::from_str_radix(&str::replace(out, "_", ""), 8),
+    )
+    .parse(input)
+}
+
+fn binary(input: &str) -> IResult<&str, isize> {
+    map_res(
+        preceded(
+            alt((tag("0b"), tag("0B"))),
+            recognize(many1(terminated(one_of("01"), many0(char('_'))))),
+        ),
+        |out: &str| isize::from_str_radix(&str::replace(out, "_", ""), 2),
+    )
+    .parse(input)
+}
+
+fn decimal(input: &str) -> IResult<&str, isize> {
+    map_res(
+        recognize((
+            opt(one_of("+-")),
+            many1(terminated(one_of("0123456789"), many0(char('_')))),
+        )),
+        |out: &str| str::replace(out, "_", "").parse::<isize>(),
+    )
+    .parse(input)
+}
+
+fn decimal_str(input: &str) -> IResult<&str, &str> {
+    recognize(many1(terminated(one_of("0123456789"), many0(char('_'))))).parse(input)
+}
+
+pub fn parse_integer(input: &str) -> IResult<&str, OwaAst> {
+    let (input, value) = (alt((hexadecimal, octal, binary, decimal))).parse(input)?;
+    Ok((input, OwaAst::int(value)))
+}
+
+pub fn parse_float(input: &str) -> IResult<&str, OwaAst> {
+    let result = map_res(
+        alt((
+            // Case one: .42
+            recognize((
+                opt(one_of("+-")),
+                char('.'),
+                decimal_str,
+                opt((one_of("eE"), opt(one_of("+-")), decimal_str)),
+            )), // Case two: 42e42 and 42.42e42
+            recognize((
+                opt(one_of("+-")),
+                decimal_str,
+                opt(preceded(char('.'), decimal_str)),
+                one_of("eE"),
+                opt(one_of("+-")),
+                decimal_str,
+            )), // Case three: 42. and 42.42
+            recognize((opt(one_of("+-")), decimal_str, char('.'), opt(decimal_str))),
+        )),
+        |out: &str| -> Result<OwaAst, std::num::ParseFloatError> {
+            let result = out.parse::<f64>()?;
+            Ok(OwaAst::float(result))
+        },
+    )
+    .parse(input)?;
+    Ok(result)
+}
+
+#[test]
+fn test_integer() {
+    // decimal
+    assert_eq!(parse_integer("12garbage"), Ok(("garbage", OwaAst::int(12))));
+    assert_eq!(parse_integer("12"), Ok(("", OwaAst::int(12))));
+    assert_eq!(parse_integer("-12garbage"), Ok(("garbage", OwaAst::int(-12))));
+    // assert_eq!(integer("-12"), Ok(("", OwaAst::int(-12))));
+
+    // hexadecimal
+    assert_eq!(parse_integer("0x12"), Ok(("", OwaAst::int(0x12))));
+    assert_eq!(
+        parse_integer("0x12garbage"),
+        Ok(("garbage", OwaAst::int(0x12)))
+    );
+    // assert_eq!(integer("-0x12"), Ok(("", OwaAst::int(-0x12))));
+    // assert_eq!(
+    //     integer("-0x12garbage"),
+    //     Ok(("garbage", OwaAst::int(-0x12)))
+    // );
+
+    // octal
+    assert_eq!(parse_integer("0o12"), Ok(("", OwaAst::int(0o12))));
+    assert_eq!(
+        parse_integer("0o12garbage"),
+        Ok(("garbage", OwaAst::int(0o12)))
+    );
+    // assert_eq!(integer("-0o12"), Ok(("", OwaAst::int(-0o12))));
+    // assert_eq!(
+    //     integer("-0o12garbage"),
+    //     Ok(("garbage", OwaAst::int(-0o12)))
+    // );
+
+    // binary
+    assert_eq!(parse_integer("0b10"), Ok(("", OwaAst::int(0b10))));
+    assert_eq!(
+        parse_integer("0b10garbage"),
+        Ok(("garbage", OwaAst::int(0b10)))
+    );
+    // assert_eq!(integer("-0b10"), Ok(("", OwaAst::int(-0b10))));
+    // assert_eq!(
+    //     integer("-0b10garbage"),
+    //     Ok(("garbage", OwaAst::int(-0b10)))
+    // );
+}
+
+#[test]
+fn test_float() {
+    // normal
+    assert_eq!(parse_float("12."), Ok(("", OwaAst::float(12.0))));
+    assert_eq!(parse_float("12.0"), Ok(("", OwaAst::float(12.0))));
+    assert_eq!(parse_float("-12.0"), Ok(("", OwaAst::float(-12.0))));
+    assert_eq!(parse_float("12.garbage"), Ok(("garbage", OwaAst::float(12.0))));
+    assert_eq!(
+        parse_float("12.0garbage"),
+        Ok(("garbage", OwaAst::float(12.0)))
+    );
+    assert_eq!(
+        parse_float("-12.0garbage"),
+        Ok(("garbage", OwaAst::float(-12.0)))
+    );
+
+    // with exponent
+    assert_eq!(parse_float("12.0e12"), Ok(("", OwaAst::float(12.0e12))));
+    assert_eq!(
+        parse_float("12.0e12garbage"),
+        Ok(("garbage", OwaAst::float(12.0e12)))
+    );
+    assert_eq!(parse_float("-12.0e12"), Ok(("", OwaAst::float(-12.0e12))));
+    assert_eq!(
+        parse_float("-12.0e12garbage"),
+        Ok(("garbage", OwaAst::float(-12.0e12)))
+    );
+}
diff --git a/src/parser/quote.rs b/src/parser/quote.rs
new file mode 100644
index 0000000..ce87fa4
--- /dev/null
+++ b/src/parser/quote.rs
@@ -0,0 +1,24 @@
+use nom::{IResult, Parser as _, bytes::complete::tag, combinator::map, sequence::preceded};
+
+use crate::parser::{OwaAst, parse_value};
+
+pub fn parse_quote(input: &str) -> IResult<&str, OwaAst> {
+    map(preceded(tag("'"), parse_value), OwaAst::new_quote).parse(input)
+}
+
+#[test]
+fn test_keyword() {
+    assert_eq!(parse_quote("'foo"), Ok(("", OwaAst::sym("foo").to_quote())));
+    assert_eq!(
+        parse_quote("':foo1232"),
+        Ok(("", OwaAst::kw("foo1232").to_quote()))
+    );
+    assert_eq!(
+        parse_quote("'\"foo\":s"),
+        Ok((":s", OwaAst::str("foo").to_quote()))
+    );
+    assert_eq!(
+        parse_quote("''[\"foo\"]:s"),
+        Ok((":s", OwaAst::str("foo").to_vec().to_quote().to_quote()))
+    );
+}
diff --git a/src/parser/set.rs b/src/parser/set.rs
new file mode 100644
index 0000000..24c5618
--- /dev/null
+++ b/src/parser/set.rs
@@ -0,0 +1,29 @@
+use nom::{IResult, Parser as _, combinator::map};
+
+use crate::parser::{OwaAst, collection};
+
+pub fn parse_set(input: &str) -> IResult<&str, OwaAst> {
+    map(collection("#{", "}"), OwaAst::set).parse(input)
+}
+
+#[test]
+fn test_set() {
+    assert_eq!(
+        parse_set("#{:a :b :c}"),
+        Ok((
+            "",
+            OwaAst::set([OwaAst::kw("a"), OwaAst::kw("b"), OwaAst::kw("c")])
+        ))
+    );
+    assert_eq!(
+        parse_set("#{:a [:b #{\"c\"}] [(:d)]}garbage"),
+        Ok((
+            "garbage",
+            OwaAst::set([
+                OwaAst::kw("a"),
+                OwaAst::vec([OwaAst::kw("b"), OwaAst::set([OwaAst::str("c")]),]),
+                OwaAst::vec([OwaAst::call([OwaAst::kw("d"),]),])
+            ])
+        ))
+    );
+}
diff --git a/src/parser/string.rs b/src/parser/string.rs
new file mode 100644
index 0000000..806fb1d
--- /dev/null
+++ b/src/parser/string.rs
@@ -0,0 +1,96 @@
+use nom::combinator::opt;
+use nom::{IResult, Parser};
+
+use nom::{
+    bytes::complete::{escaped, tag},
+    character::complete::{none_of, one_of},
+    combinator::map_res,
+    sequence::delimited,
+};
+
+use crate::parser::OwaAst;
+
+fn unescape_string(s: &str) -> Result<String, String> {
+    let mut result = String::new();
+    let mut chars = s.chars();
+
+    while let Some(ch) = chars.next() {
+        if ch == '\\' {
+            match chars.next() {
+                Some('n') => result.push('\n'),
+                Some('r') => result.push('\r'),
+                Some('t') => result.push('\t'),
+                Some('b') => result.push('\x08'),
+                Some('f') => result.push('\x0C'),
+                Some('\\') => result.push('\\'),
+                Some('"') => result.push('"'),
+                Some(c) => {
+                    return Err(format!("Unknown escape sequence: \\{c}"));
+                }
+                None => {
+                    return Err("Unexpected end of string after backslash".to_string());
+                }
+            }
+        } else {
+            result.push(ch);
+        }
+    }
+
+    Ok(result)
+}
+
+pub fn parse_string(i: &str) -> IResult<&str, OwaAst> {
+    let (input, value) = delimited(
+        tag("\""),
+        opt(map_res(
+            escaped(none_of("\"\\"), '\\', one_of("\"\\nrtbf")),
+            unescape_string,
+        )),
+        tag("\""),
+    )
+    .parse(i)?;
+    Ok((input, OwaAst::str(value.unwrap_or_else(String::new))))
+}
+
+#[test]
+fn test_symbol() {
+    assert_eq!(parse_string("\"foo\""), Ok(("", OwaAst::str("foo"))));
+    assert_eq!(
+        parse_string("\"foo1232\""),
+        Ok(("", OwaAst::str("foo1232")))
+    );
+    assert_eq!(
+        parse_string("\"foo\"garbage"),
+        Ok(("garbage", OwaAst::str("foo")))
+    );
+    assert_eq!(
+        parse_string("\"foo\\\"bar\"garbage"),
+        Ok(("garbage", OwaAst::str("foo\"bar")))
+    );
+    // Test newline escape
+    assert_eq!(
+        parse_string("\"hello\\nworld\""),
+        Ok(("", OwaAst::str("hello\nworld")))
+    );
+    // Test tab escape
+    assert_eq!(
+        parse_string("\"tab\\there\""),
+        Ok(("", OwaAst::str("tab\there")))
+    );
+    // Test backslash escape
+    assert_eq!(
+        parse_string("\"path\\\\file\""),
+        Ok(("", OwaAst::str("path\\file")))
+    );
+    // Test carriage return
+    assert_eq!(
+        parse_string("\"line\\rend\""),
+        Ok(("", OwaAst::str("line\rend")))
+    );
+
+    // Test space
+    assert_eq!(
+        parse_string("\"hello world\""),
+        Ok(("", OwaAst::str("hello world")))
+    );
+}
diff --git a/src/parser/symbol.rs b/src/parser/symbol.rs
new file mode 100644
index 0000000..924447e
--- /dev/null
+++ b/src/parser/symbol.rs
@@ -0,0 +1,22 @@
+use nom::{IResult, Parser as _, combinator::map};
+
+use crate::parser::{OwaAst, identifier};
+
+pub(super) fn parse_symbol(input: &str) -> IResult<&str, OwaAst> {
+    map(identifier, OwaAst::sym).parse(input)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn symbol() {
+        assert_eq!(parse_symbol("foo"), Ok(("", OwaAst::sym("foo"))));
+        assert_eq!(parse_symbol("foo1232"), Ok(("", OwaAst::sym("foo1232"))));
+        assert_eq!(
+            parse_symbol("foo:garbage"),
+            Ok((":garbage", OwaAst::sym("foo")))
+        );
+    }
+}
diff --git a/src/parser/unquote.rs b/src/parser/unquote.rs
new file mode 100644
index 0000000..3f7aaa4
--- /dev/null
+++ b/src/parser/unquote.rs
@@ -0,0 +1,27 @@
+use nom::{IResult, Parser as _, bytes::complete::tag, combinator::map, sequence::preceded};
+
+use crate::parser::{OwaAst, parse_value};
+
+pub fn parse_unquote(input: &str) -> IResult<&str, OwaAst> {
+    map(preceded(tag("$"), parse_value), OwaAst::new_unquote).parse(input)
+}
+
+#[test]
+fn test_keyword() {
+    assert_eq!(
+        parse_unquote("$foo"),
+        Ok(("", OwaAst::sym("foo").to_unquote()))
+    );
+    assert_eq!(
+        parse_unquote("$:foo1232"),
+        Ok(("", OwaAst::kw("foo1232").to_unquote()))
+    );
+    assert_eq!(
+        parse_unquote("$\"foo\":s"),
+        Ok((":s", OwaAst::str("foo").to_unquote()))
+    );
+    assert_eq!(
+        parse_unquote("$$[\"foo\"]:s"),
+        Ok((":s", OwaAst::str("foo").to_vec().to_unquote().to_unquote()))
+    );
+}
diff --git a/src/parser/vector.rs b/src/parser/vector.rs
new file mode 100644
index 0000000..d3a2567
--- /dev/null
+++ b/src/parser/vector.rs
@@ -0,0 +1,29 @@
+use nom::{IResult, Parser as _, combinator::map};
+
+use crate::parser::{OwaAst, collection};
+
+pub fn parse_vector(input: &str) -> IResult<&str, OwaAst> {
+    map(collection("[", "]"), OwaAst::vec).parse(input)
+}
+
+#[test]
+fn test_vector() {
+    assert_eq!(
+        parse_vector("[:a :b :c]"),
+        Ok((
+            "",
+            OwaAst::vec([OwaAst::kw("a"), OwaAst::kw("b"), OwaAst::kw("c"),])
+        ))
+    );
+    assert_eq!(
+        parse_vector("[:a [:b :c] [[:d]]]garbage"),
+        Ok((
+            "garbage",
+            OwaAst::vec([
+                OwaAst::kw("a"),
+                OwaAst::vec([OwaAst::kw("b"), OwaAst::kw("c"),]),
+                OwaAst::vec([OwaAst::vec([OwaAst::kw("d"),]),]),
+            ])
+        ))
+    );
+}